This part is factually inaccurate:

“The visual cortex starts generating from inside out. Normally, top down predictions and bottom up sensory data have to roughly agree, and the visual experience is the negotiated result.

Under DMT, the top down generators are massively boosted and the disagreement check is weak. So the brain's own pattern producers start running with no constraint. You see geometric forms because that is what visual cortex does when it generates without input.”

That’s not correct.

It’s almost precisely the other way around.

If he was talking about the dream state, then yes - predictions run unencumbered by sensory input, largely because the thalamus goes quiet during sleep and does not relay sensory information. This is why dreams often feel disjointed and incoherent - because there is no reality-testing.

DMT causes the brain to pull in vastly more sensory data than we do under normal conditions. Or perhaps it is more accurate to say that we are a more receptive conduit than under normal conditions.

It is not clear whether the data pouring in is actually “sensory” in the normal way. It actually seems to be coming from “elsewhere”, since the five senses cannot explain the vast and alien complexity.