Your anecdote is for an unrelated substance that isn't even a psychedelic. As for accepting anything as true I've actually said repeatedly that parapsychology has produce evidence that has justified continued research at the academic and personal level but has no definitive smoking guns.
But there is a lot of interesting evidence that compares psychedelic experiences with other reported phenomenon that deals with paranormal encounters. I look at it in the same way I do possession.
As for what the signifier materialist points to, I'd say it's really more about a separation of the Phenomenal and the Physical, and holding to the idea that Physical -> Phenomenal. The alternatives are
Panpsychism (Physical & Phenomenal are both part of reality's firmament),
Idealism (Phenomenal -> Physical), and
Neutral Monism (Fundamental Substance -> Physical & Phenomenal).
Relating this back to the topic (I'm putting in links to show I'm not just sitting around making this stuff up as a I go along):
Materialists would suggest that any insights are not due to supernatural communication but rather to the abilities of psychedelics and other drugs like MDMA to shift neuronal pathways or block parts of the brain responsible for addict cravings. Basically something like rebooting and scrubbing of the software.
Laher, for example, has tons of hyper-real experiences but never wavers from his belief in materialism. That said, he discusses the insights the drugs allowed him to make, and really a good deal of the
benefits of therapy via these drugs doesn't vanish if you're a materialist.
Panpsychists could suggest that conscious matter retains the memories of plants and this is communicated in what seems like a different realm. We might look at
Goff's idea that superimposed particles of experience drive the mental causation of physical forms, along with Lanier's idea of how
post-symbolic (alphabet/word based) communication in Virtual Reality might work. The plants are trying to tell us things but their understanding of time-space is far greater than our own so attempts to communicate in what might be post-symbolic, sensory grounded language trumps our understanding.
Idealists might point to the (contested) decrease in brain activity as a sign that the brain "
as a knot of consciousness", actually filters the greater Mind all things are a part of. So the spirits are always around, but our minds have filtered them out. The drugs then are a means for us to experience anamnesis - "loss of forgetfulness" - and utilize the claim
consciousness is not restricted in space (Mind -> Space-Time) to "travel" to other realities that are really "here".
Neutral Monists would likely have a variety of ideas connected to all the above concepts. Perhaps Strassman's
theoneurological model is what connects people to the Truth that Phenomenal & Material spring from God
who grounds all Being.