Thanks for the explcit reference to the lore. In my new PT, I arrived at the end of act 2 again, and the first encounter with the emperor and Orpheus. The emperor states very clearly that Gith made the pact with Tiamat during the revolt against the Ilithid, which Lae'zel confirms. The emperor also claims that Gith had the power to disrupt the hivemind, a power which was passed on to her son Orpheus.
So BG3 has modified this lore with respect to DND 2E.
To be fair, AD&D 2nd Edition was full of contradictory material since the game designers weren't allowed to do any major testing from the mid-1980s, and many products were rushed out and created by different teams. It was very liberating to drive our home campaign past the official timeline, because I can now just choose which information is true in my multiverse and not get contradicted by future products that chose differently. To me, BG3's narrative too was a DM making such decisions and as a gamer I simply accepted differences to my campaign, like - "okay, there are no firearms in your world." I would also say that most of the other character species in my world are far less human than how Larian depicted them. Besides obvious design flaws, role-playing games often leave the last decision to the one writing the adventure. Since I'm usually exclusively a DM, it was nice to just be a player again.
