I also think, this is a missed opportunity of an interesting quest involving freeing those drow and talking to them after the spectator is killed by your party. Like that it's just another mob battle.
Nevertheless it would be reasonable that those drow act hostile to you, since they were about to attack the Selunite Temple, when they were turned into stone. Since your party is full of overworld beings most likely including your own character, the drow would think you belong to the Selunites and were sent here to repell the attack. Anyway some talking with the drow and different options, how to manage that encounter would be very much appreciated.
But they attack not because of this, but because of Beholder "charm" , which does not off even after his death. I really hope there is a dialogue, it's just not ready yet.