Psilocybin was way different than 4-AcO-DMT for me, or any other 4-sub for that matter. The visual effects were unlike anything I've encountered since, almost like viewing the world through a distorted fish-eye lens. Completely devoid of color, everything took on shades of dark grey. It also felt much more insightful and more stripping of cultural associations. 4-AcO-DMT felt much dreamier and more like the other 4-subs I've tried.
I saw a study where psilocybin cannot be detected in the bloodstream when taken orally (first blood samples taken 15 minutes in), so I question how much of a pharmacological difference there is here. Definitely would help to better understand the activity of other alkaloids present as
@arrall suggested.
From a REBUS perspective it makes sense that plant material vs. powder could lead to differently perceived experiences even if the active components are the same. Once you start relaxing a lot of other high-level beliefs, suddenly the distinction between a plant and powder gains influence and could more strongly impact how the experience is interpreted/constructed. Although for many people the distinction of plant vs. powder probably carries a large influence to begin with.
The sentiment I've encountered is that esterases are present in the bloodstream, and if their concentration and/or rate is high enough, you still wouldn't have a significant amount of the ester reaching the brain. Succinylcholine administered IV is 90-95% hydrolyzed before it reaches tissue, so the reaction can happen quickly, at least in some cases.
Interesting paper in 2020 on 4-sub SAR showed that 4-AcO-DPT and 4-AcO-MPT are more potent in mice than their hydroxy counterparts. To your point, this can't be explained if the ester was rapidly hydrolyzed, so at the very least there can be significant differences in AcO vs. HO brain uptake (caveat: species differences exist w.r.t esterase activity). They also showed the AcO esters of all major 4-subs have 5-HT2A Gq efficacy, although it was generally over an order of magnitude weaker than the corresponding hydroxy.
At least for the AcO's vs. HO's, this supports the notion that there is a distinction and that it might not just be kinetic either.