I believe it. There was a steamcommunity post last year detailing all the cut content. I believe some of it has been added back through the patches (I only played through the game once, around launch).
To me the tadpole consequences is the most egregious, as the whole system and decisions connected to it feel so hollow when they end up not mattering at all.
Yeah, stuffing more worms into your brain being purely a beneficial mechanic with no drawbacks is a very weird choice. This whole system was honestly better in early access than it ended up being, having the tadpoles be just a dialogue option with a very easy check but consequences the more you used them. The ring that Omeluum gives you was even supposed to help, only to get changes into a boring Charm resistance ring on release.
I don't know if it's been culled by now in patches, but when I played there were still lines by the narrator talking about the consequences and "if you do this, there's no going back" regarding the brain worms. All lies, it turns out.
I have no clue why they cut it, but having it actually impact your potential choices and your endings would be thematically appropriate and make for fun and difficult gameplay choices, I would have thought.
The lack of consequences for the brain worms - and lack of rewards or even mentions for abstaining! - was part of why Act 3 soured me on the game quite a bit. Come on, not even a silly achievement for not using any Illithid power all playthrough?
Yeah, I was very dissapointed by that as well. As far as I'm aware, the only time it matters is when
Act 3 spoiler
The Emperor offers you the Astral tadpole, if you used any worms you have to pass a check that grows harder the more worms you consumed to resist using it, if you abstained you can just say no.
Yeah but even that is pointless because there are literally zero consequences to accepting the Astral Tadpole! Even though you're half Illithid supposedly it all kinda just goes away in the happy ending. I don't get it.
Furthermore, there is an option to destroy the special "gift" if you can resist accepting it. However, all you get for doing so is a few brief lines from the Emperor. Your companions don't seem to notice, and there isn't even an quest log update.