The key point here:
THE PULSE: How do you approach something so expansive as a History of the Multiverse? How do you research something like this?
JURGENS: It's researched via my own memory and a massive stack of comics that are sitting here. Again, we're hitting the high points here, in so far as the other universes go.
THE PULSE: What will each part of this be exploring?
JURGENS: I think the best way to approach this is with some sense of chronological order, starting with the first time two universes interacted. This happened, of course, when Earth-1's Flash inadvertently traveled to Earth-2.
So I guess that means that All of our old comics are now back in canon?
Probably, after the Megaverse is added all DC comics will be back in canon. It's a long, 7 years!, explanation for essentially the hypertime concept.
You know what's funny? What made DC unique the last twenty plus years was the singleverse. Now, DC appears to be adapting Marvel's working multiple universe model. Not that I'm complaining or anything, just a thought.