It is during Secret Wars. I was saying that it was post-Incursion.
They don't think they're on a new earth. Battleworld is the only "Earth" they know. For whatever reason, one that may be revealed soon, these characters don't know anything about "616" or "1610" or even "Earth." They know that Doom is their god, that travel between regions is illegal, and that the portal did something that won't make Doom happy.
The simpler answer is just that they're either mind wiped or new creations of Doom that used 1610 and 616 as templates. The idea that these "Ultimate" characters were plucked from some pre-Incursion time of UU history is just too convoluted, and only opens up more problems.