What gets a little mind bending for me is the idea that the physics inside the black hole can differ slightly from the ancestor universe. So black holes will preferentially create descendant universes that prefer to create more black holes.
This is a different multiverse theory than the quantum many worlds theory. The limitation of quantum many worlds is that the physics doesn't change. But in the ancestor black hole many worlds theory it does.
When you put these together, you can get an even larger multiverse, where anything that can happen does happen, but only if the laws of physics allow for black holes. That may mean the Marvel Cinematic Universe, is out there somewhere, so long as those laws of physics allow for black holes. Right? Again not a physicist.