Why Does Earth Two Look Like Flashpoint?

What is James Robinson’s and Nicola Scott’s Earth Two comic really about? The official line is, it was originally to be titled Justice Society. We know that Worlds’ Finest is about the Earth Two Power Girl and Huntress (who is confirmed as the daughter of Batman and Catwoman, per the original concept of the character) getting trapped in whatever DC is calling its main dimension. But I don’t think anybody’s ever said Earth Two was necessarily going to be where the superheroes started out in World War II. Like most people, I’d just been assuming that was what they were talking about, and then DC releases an alternate cover for the first issue: