No, that's not how copyright laws work. Especially in a world where the starting point is the accused making something and marketing it as someone else's IP with a license change.

It's still on the claimant to establish copying, which usually involves showing that the two works are substantially similar in protected elements. That the defendants had access to the original helps establish copying, but isn't on its own sufficient.

Only after that would the burden be on the defendants, such as to give a defense that their usage is sufficiently transformative to qualify as fair use.