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.
Big shame that’s all that remains of this system.
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.
As I recall there are two decisions. First you get the choice of the Astral Tadpole, which opens the outer ring of mindflayer powers and gives you black veins in your face and the status “half-Illithid”.
Later - as part of the ending - you can decide to become a full on mindflayer, because for some arbitrary narrative reason the mcguffin can only be operated by one.