Suppose a model of reality M (which makes predictions) and doesn't admit a higher metaphysical plane as part of the model. Now assume Mp does admit a higher metaphysical plane and makes the same predictions as M for all observable phenomena (or for all reality in the sense of 'this reality').
In such a case, the existence of a higher metaphysical plane is purely aesthetic. In terms of predictions, both models are equally correct, being identical. The correctness of the internal representation is beyond epistemological limits, and arguably a meaningless or ill-formed proposition. For a significant difference, the models must make different predictions. But the conventional understanding (say the standard model) is carefully constructed and deviations by laypeople are invariably simplifications or are due to impaired reality testing.
This situation is the same as religion, because it is one. Either the religion doesn't make predictions about reality, in which case it's difference is purely aesthetic (as a model of reality), or it does and in practice is either trivially falsifiable or copying what is already known (note that the old well known religions have long since had their predictions tested).
Psychedelic experiences could, in theory, produce interesting hypotheses about reality; just like Scientology and the "Twin flame" people could. But in practice it almost always seems to produce crackpot stuff like "you can make a perceptual motion machine with time crystals and fractals; also Einstein, Aristotle, and Tupac already knew this but no one was paying attention; luckily drug-induced divine revelation has bequeathed this information via direct transmission; if only everyone else experienced ego death, then maybe they could be as great as I".
This is the hubris I perceive in the idea that scientists, philosophers, etc. that have dedicated their life to the study of particular tiny pieces of reality and honed a disciplined sense of intellectual rigor are going to be outdone by random people tripping. It is uniquely offensive and arrogant.
That said, in so far as 'reality' is 'my model of reality', individuals may gain psychological insight by partaking in 'spiritual' activity, including psychedelics, and it follows that they may gain a 'special understanding of (their) reality' in that way. The problems are the magical thinking implicated in universalizing personal insight, the pitfall of assuming independence of realities beyond subjective experience, the belief subjective perception is unlimited by physical reality, and in some a tendency to insist that such insight cannot be gained in other (more mundane) ways.