> Can you only reflect while high?
Personally, yes; at least effectively.
> It may be that the initial psychedelic sessions
I had a few experiences with mushrooms in my youth, so I know what you mean - but cannabis isn't psychedelic.
Cannabis is psychedelic to the extent that the term means anything. It's not a "classic" psychedelic like acid or shrooms, but there is no obvious category difference between microdosing shrooms vs. smoking a joint vs. having a proper trip vs. greening out, and so on. It's all spectrums of psychedelic experience caused directly by something you ingested.
The opposition to the term likely has more to do with proponents and lobbyists wanting to distance weed from the "harder" psychedelics that are known to fry people.
The terms here get kinda vague and smushy. I wouldn't necessarily call cannabis psychedelic, but i would call it a hallucinogenic. And very high doses of weed, especially edibles will give you closed eye visuals and auditory hallucinations. It's certainly not the same as LSD, but it's not entirely separate either.