Ah, makes sense, I read them after a DM told me to read them to prepare for campaign and he is a pretty heavily planescape influenced guy, who almost always runs his cosmos the planescape way.
Anyway, enough about that, as its starting to go off-topic.
But on a related on-topic note:
I hate worlds where the books establish a creation myth as being the canon truth, while there is no way that people inside the world would actually know if it was true.
Think oWoD was guilty of this; Reading the VtM books made it pretty clear that the real creation myth was very close to the judeo-Christian creation myth with a few spins on it.
There was no reason any characters in the game world would have more certainty about it than characters from our world, but by establishing it as almost a fact in the canon, I had players who would get upset if there was any hint ingame that creation happened another way