Well, the thing about the "everything happens in infinity" premise that the comics seem to be using is that it includes everything
everything. So even a fictional story told by a character in one universe is going to be real somewhere in the infinite multiverse, according to this line of thought. Because even the most incredibly unlikely thing, like reality exactly conforming to somebody's work of fiction, will inevitably happen if you give it an infinite number of chances. That's why a lot of people like that idea, and why others, like me, dislike it: because it's a handy excuse to justify any cockamamie notion no matter how absurd it seems.