"Thanks for your hemp ShamensStamen." lol, i had to laugh.
Also, i'm not referring to the visuals or anything, i'm talking about the effects of Psychedelics in general, there's definitely a Glutamatergic aspect there, and the Serotonin 2A to Metabotropic Glutamate 2 receptor complex could be the link you're looking for, as Psychedelics by activating the Serotonin 2A receptor within that complex, also interacts with the Metabotropic Glutamate 2 receptor which probably causes some Glutamatergic effects which could quite possibly lead to some similar effects as NMDA antagonists. I think a large part of the Psychedelic experience is Glutamatergic, which is why there are similarities, but also differences, compared to anti-Glutmatergics. It could be that the Psychedelics activate the Metabotropic Glutamate 2 receptor, or they antagonize, or otherwise modulate it, so that could potentially lead to some dissociative states.
As for not getting OBE's with Psilocin, how much have you taken so far of mushrooms? I've worked with DMT a lot, mostly orally with Harmalas/Rue or Moclobemide, but also a good bit of Harmala-heavy Changa, have had LSD a few times (up to 3 hits), had up to 2 hits of 25-D Nbome a couple times, and have had a handful of mushroom, as well as 4-ACO-DMT experiences with and without MAO-A inhibition using Harmalas/Rue or Moclobemide, and i've never had an OBE, though with the oral DMT i have had one moment where my body went completely numb, all i could feel was this sensation on my forehead, i saw a bright white light that was there with eyes closed and open, and it completely took me over/consumed me, then i threw up and slowly came back down. Have had plenty of death/dying experiences, but rarely ever see closed eyed visuals or visions, i've only had one vision on Pharmahuasca and that was a precognitive vision about my dad's death that came true 2 weeks later. So for me, most of what Psychedelics do are mental, physical, emotional and spiritual, rarely visual.
But yeah as far as being dissociated on DMT goes, never had that personally, no matter how much i've consumed (still haven't tried pure vaped DMT yet, but i will sometime or another), i've always felt sane, relatively sober but definitely altered lol, clear headed, aware, i've always felt in my body, my surroundings never disappeared or anything like that, and i've had some strong dosages of oral DMT (using Mimosa and Acacia root) and Changa.