Initially, things seemed fine and fairly mundane. Then they introduced angels down the line, with mention of some angels being "only" six thousand years old (possibly hinting at Young Earth Creationism). Then they showed that non-Jehovah deities existed (EG: Odin, Ganesh, et cetera) and pre-dated Jehovah, which really threw a monkey-wrench into things. Then they had a being show up from Purgatory (generally regarded as a Jehovah construct) who pre-dated angels by about four thousand more years. In the episodes I started watching last night, some more folks were brought out of Purgatory who pre-dated both the creation of mankind and the creation of angels (which gets extra screwy, since it's generally accepted that angels assisted creation of the universe). Oh, and Death-as-a-being pre-dates everything.
Obviously, a little bit of a muddle.
But! But! Last night I had an epiphany!
It's been shown that angels can go back and mess with history, making a new "now" with only other divine beings being aware of the fact that history was messed with. If an angel can do it, a full-on deity should be able to, as well.
My current hypothesis is that when a given deity is in power, they tend to come up with their creation story, then go back in time and make reality match their story (with only other divine beings being in on the fact that it wasn't always that way).
This way, you get to have a fairly literal Young Earth Creationism gig going on, while also having all the other pantheons' stories being equally true in the greater scheme of things.