You are getting the bossq drop, but not for the reason you are thinking. With the a1q6 set up, the flags going into it the first time will not have the 'killed andariel' one set. Since it is not set you will get the bossq type of drop when you kill her and the game will set the sub flag 'killed andariel', but the quest is not done at that point. You still need to go talk to one of the NPCs with a "!" and that will trigger the last portion of the quest to complete it. Part of that completion process is change some of the flags for the quest, including the 'killed andariel' flag back to an uncompleted status (it really did not matter in the earlier versions as a different flag is being used to denote the entire quest is done). But since this is the only flag being checked for determining which of the two drops to use, any time further that you kill her, the game will check that sub flag and see that it is not in the 'set' position and in turn give you the bossq type of drop.