Wasn't the whole point of Convergence that Pre-Flashpoint Brainiac went back in time and bottled cities from every important alternate timeline or universe in the history of the Multiverse and Hypertime before they got destroyed, then restored them to full universes in the present of the regular universe? In fact, the Flashpoint timeline was one of the specific ones mentioned. So to anyone reading, the answer to this mystery was already told years. ago. I suppose the bit could still be the character's solving the mystery, but somehow I bet what will instead happen is they give a completely different explanation than the one that was already given in Convergence. Of course, technically the universes created in Convergence are from splintered off timelines from Brainiac grabbing the cities and bringing them elsewhere, so you could say the original also survived for a reason separate from Brainiac, but then it should be missing the city that Brainiac bottled, which it almost surely won't be. No, what will probably happen is no reference to Convergence at all. Technically some autist, such as myself, could still justify this by saying it's a completely separate timeline that just happens to be exactly like the Flashpoint timeline, but that's stupid, even if technically possible.