I believe I have an explanation that covers some of the territory here. I don't claim it covers all of the phenomenon in question. Hopefully it will be of some benefit in clearing up certain confusions.
In order to have the necessary insights, practitioners engage in cultivation of prerequisite skills. One long lived and fairly straightforward model of such skills is the 7 Factors of Enlightenment:
- Physical Relaxation
- Determination to Investigate
Depending on where a person starts (existing linkages between beliefs and values) they may be led to come up with a variety of ideas about the 'true nature of reality' along the way as these linkages change. Even if this map-territory error isn't made, a significant and unexpected shift in how you relate to your own life, ie the story you use to make sense of your current belief-values stack, can be a lot to take on. The urge to 'make-sense-of' intermediate steps in the refactoring process can be very strong.
Imagine a big network of beliefs and values. Let's say that our attention has been drawn to one particular cluster that handles some aspect of our life. It might be financial security, physical well being, relating to others, etc. One of the things that seems to happen is that, in the course of practice, we learn that one particular type of linkage isn't true. I'll give the concrete example of the assumption that if you hear someone say something, it means they really believe it. This might sound bit silly when stated explicitly like that, but it's definitely a linkage that can be floating around in subtle, unexamined patterns. Now, let's say you have, in the course of contemplative practice, an insight related to this linkage. After having this insight, you start noticing this linkage come up in subtle ways in all sorts of situations. Having seen it as false, there is the feeling that you are reevaluating some assumptions you had about these various situations. You're 'clearing out' these false linkages as you find them, as life presents you with situations that activate various areas of your belief-values network and you notice various instances of the linkage.
Having this as a basic picture we can start to make sense of some of the things that happen to people as they have various insights. Let's say you had a whole cluster of beliefs around, say, religion. You can imagine that these beliefs were tied to the rest of the network via all sorts of linkages. As insight occurs and more and more false-linkages are pruned away, various chunks of the network can come off in idiosyncratic order as life presents you with situations that draw your attention to various parts of the network. If a bunch of 'values' based linkages fall away, it can lead to feelings of meaninglessness or, at the other end of the spectrum, intense affective activation, positive or negative. If a bunch of 'belief' based linkages fall away, it can literally feel like reality is dissolving. This is much much more literal than many people will be willing to believe before it happens, especially if they have little to no drug experience. When this happens with parts of the network that are involved with the visual system, for instance, the visual field can actually dissolve into a bunch of vibrations temporarily as you refactor parts of the network related to extremely low level things like edge or motion detection (this is also where 'auras' come from imo).
We used a fairly mundane examples, but you might be able to imagine that this can get pretty disorienting when it involves things you assumed were immutable (the classic example of course being changes in the sense of self). This is one of the big reasons equanimity is considered such a core skill for this process to unfold without causing undue distress. This process can have a poor interaction with a particular personality type. The sort of person who, upon being given a screwdriver, runs around compulsively disassembling everything they can find that was built with screws. It could also be framed as the same sort of tendency that lends one to completionism in video games combined with the addictive quality of insights. The felt sense that The Big Answer is just around the corner. The one that will finally give us the power to arrange the world to meet our neglected needs.
I think it's useful to note that the range of insights is truly vast. In fact, the Theravadans say 'insight is infinite' because the range of skillful action in the world is so vast. You won't be able to 100% this save file any time soon, so you can relax and be a bit more methodical, strategic and skeptical as you go. You saw through a false linkage. Great! But before you go running off to evangelize to others, realize that your new realization is only slightly better. This doesn't mean it isn't helpful to talk about such things with others. Some other people may be at a similar enough stage in their network refactoring that they derive great benefit from what you share. Recognize also this tendency in others, to evangelize at you parts of the process that are particularly salient to them due to their path up the mountain. "Holy shit, I fell into that crevasse and broke my leg and it was a year before I managed to heal and climb out. Everyone needs to know about that and anyone who doesn't emphasize it is irresponsible." But the mountain is large, people are climbing it from many sides and using many techniques. Some are insistent that you need a particular kind of rope, some are obsessed with first aid for the particular kinds of injuries they or a friend sustained, some are trying to build wheelchair accessible ramps up to the parts of the mountain they think are best. Additional metaphors here. Bonus points for noticing the ways this post itself could be an example of the thing.
Making sense of the intermediate steps is attractive for both good and bad reasons. It is good to find ways of making things stable so that you can continue to meet your responsibilities to others and lead a functional life. Dissolving the constructs that lead to you prioritizing exercise, eating well, and sleeping should be seen as dissolution of the goodness of the means, not the ends. E.g. you were using fear based motivation to keep you exercising, which you subsequently saw through. This doesn't mean exercise was bad, it means your method was bad and you should find an upgraded one. It is attractive for bad reasons when it involves things like showing off how clever you are. Many teacher-student groups revolve around a teacher having reified a particular set of insights and then, via selection effects, found a decent sized group of people who are at the right stage to think those insights are The Big Answer they've been looking for. Both teacher and students in this dynamic tend to stagnate. Good teachers are less concerned with particular insights and more concerned with strengthening of the process that generates insights.
These sorts of mental models are all well and good, but presumably lots of other practitioners engage with various helpful mental models as well, and many of them, maybe even most, seem to go off the rails on the claims about reality. Is there more to say about that? I have enough experience with meditation and psychedelics at this point to claim that some forms of meditation have similar effects, one of which is boosting openness to experience. In my personal opinion, shooting openness sky high without a balancing increase in healthy skepticism reliably lands you in whacky belief town. Most practitioners are not starting with solid prerequisites about map-territory distinctions, probabilistic over binary reasoning, and strong ability to demarcate is and ought (positive and normative) claims. Most schools are not, in my experience, emphasizing the very skeptical nature of the Buddha's inquiry into his own mental processing. I think the law of equal and opposite advice holds here: skeptics need a healthy dose of faith, enough to give practices an honest try. People who are riding high on a breakthrough insight (and some of them are pretty damn spectacular) need a healthy dose of skepticism. Traditionally, one waits 'a year and a day' before making claims about a particular breakthrough in order to give it time to settle and attain context within your overall progress.
Everything gets easier if you understand this to be an investigation of the map and not the territory. Making claims about reality based on the fact that your cartographic tools have changed is silly. In polishing the lens of our perception we see that it has a lot more scratches than we thought. And notice that we introduce new scratches on a regular basis, including in our efforts to polish it. "Isn't this also an example of belief?" the astute reader might ask. This is explained in the Pali Canon when the Buddha explains reaching the point that the 7 factors of enlightenment themselves are the last remaining things to be seen though. Dissolving your cartographic tools is the last thing you do on your way out.