I thought the twins were stuck somewhere in the speed force or the like
I tried to figure all this out on a Flash website (by which I mean a website about the Flash, not that it had fancy animation), and there were so many links back and forth to all sorts of events and all sorts of speed force business that I didn't know how to read it in a linear fashion. So these twins are stuck in the speed force, which, I think, has ceased to exist, and maybe they went into the future or the past or something.
Personally I liked that Secret Origins story in which, when Barry Allen raced the tachyon in Crisis, he went back in time and turned into the very bolt of lightning that gave him his superspeed in the first place. That I can understand. Now I don't even know who the Flash is.