I see the abstract point, but I don't really think it applies here. This isn't just mythic background stuff. This is a mystery campaign, and the borking of Avilona is an important part of that mystery. Then in Act 3, this becomes a fiddly bit that the PCs are asked to make a major decision over. And the GM needs the ability to adjudicate that fiddly decision. It's always risky when the PCs know more than the GM (for example, a PC has played WotBS and the GM hasn't), and then the GM has to decide the setting-impact of the PC's decision. (In this case, binding the now-dead Avilona to the cosmology, this time maybe without Jiese.) Maybe what happened in WotBS doesn't "really matter" in the designer's intent, but it does in the PC's expectation, and then you get weird disappointment or mismatched expectations, because the PC thought the GM understood what was "really going on."
For example, what if a group, on a philosophical level, decides the most ethical thing to do is to put the universe back together again as close to the original setup as possible? (Yea, I know, Reida is gone, and Av is smashed.) Is Avilona dead? Or is the pillar the problem, and *any* plane they try to connect will end up borked? (Remember, when they restored flight, it came from Badon, which was *not* in the air pillar.) I'd like slightly crisper answers to these sorts of things.
I mean, I read the material super-closely, and after a bunch of looking and forum-posts, I figured it out, and filled in the gaps with my own theories. But I could have easily have been blindsided by this at the table. Again, because it's a fiddly-bit under PC-control, I think it needs a bit of explanation.
EDIT: I say all of this because I am super-excited about the reality-hacking in this campaign (adv7 plus adv12/adv13 are just so awesome!!) and I can't get over how mindblowing-cool it is. So please excuse my passion for the subject.