From what I've read/listened to this is generally not the case. The kind of psychedelic-assisted research that's happening today uses full doses that induce a "spirtual" experience, not microdoses. I'll see if I can dig up actual links but a big source of information I have on this topic is from the fascinating and highly recommended Drug Science podcast:
https://www.drugscience.org.uk/introducing-the-drug-science-...
I remember hearing a conversation in one episode where microdose research was discussed and David Nutt, the UK's foremost neuropsychopharmacologist, said that studying full doses is more efficient from a process perspective. With such stringent rules around scheduled substances any research means a ton of red tape, keeping people under observation for ages, and so on. It's more effective to study administration of a small number of full doses than run a program to analyse a longer course of microdoses. Of course, you could probably study a one-off microdose but given the subtlety of the effects it's probably hard to distinguish the drug effects from other factors. Given the difficulty of studying this stuff at all and the belief that a full dose is necessary it makes sense to try that ahead of microdose research.
Edit: oh, quote from https://www.cell.com/cell/fulltext/S0092-8674(20)30282-8:
"The extensive use of microdosing psychedelics to putatively improve wellbeing and creativity (Kuypers et al., 2019) raises the question of whether a full psychedelic experience is needed. Microdosing involves taking—usually on a regular basis, e.g., 3 times a week—a low dose of a psychedelic that is devoid of subjective psychoactive effects. As yet there have been no trials of microdosing for any psychiatric disorder, and it seems improbable that a single microdose of psilocybin would have as big an effect in depression as the 25 mg psilocybin “macrodose” usually used. Growing evidence suggests the best outcomes from psilocybin are in patients experiencing the most powerful psychedelic effects, variously called breakthrough, peak, or mystical experiences (Roseman et al., 2018b
). [..]"
Also, Michael Pollan's book "How To Change Your Mind" goes into a lot of detail re: the therapeutic process. I'd imagine most clinical processes to be similar to the kind of stuff that happens underground now — full doses, a guide present, care on set/setting etc.