I also think that the endgame dialogue flow is slightly buggy. Last time I wanted to squid Karlach because I was on Spawn-Astarion. When the Emperor presented us with a choice, I declined Gale's offer and accepted Karlach's. After freeing Orpheus the dialogue with him offered me to volunteer Gale but had no line about Karlach. To squid Karlach, I had to volunteer myself, which then again prompted the (same) discussion with Karlach resulting in her ceremorphosis. At the brainstem I then had a long discussion with Gale about how it would be saver for everyone to explode him instead of taking up the fight against the brain together. Which might be attributed to fear, but still came out of nowhere - especially following the previous discussion.
By comparison, when I directly freed Orpheus and made him change, the game gave me intrusive thoughts about the bomb being an option at the brainstem and Gale was very happy to not use it. It's so weird. I wonder how much more buggy it would get if we could ask Omeluum to help us out.
I think, except for Shadowheart, the companion stories are cut content to some extent. Gale detonating the orb in act three doesn't explain why everyone gets cured of the tadpole (and partial illithid transformation), when Gale detonating the orb in act two causes everyone to turn into mind flayers. Considering his quest book talks about three items of Karsus: orb, crown and scepter, I'd guess that originally these were supposed to be combined into some powerful magical item. And Gale's quest was about getting the orb out of his chest.
