Just got there on my new run. His first lines are "Hurry, I've got one of those 'brain things' cornered." "There, in the grass. You can kill it it can't you? Like you killed the others."
I definitely feel he's referring to intellect devourers, not the tadpoles.
But yeah, I'm not super into the scene either, I really don't see any reason to group up with a guy who just tried to kill me. I've been thinking of just skipping the encounter, does anyone know if I will still get a second chance to recruit Astarion later if I do, like with Shadowheart?