I'm not a fan of the multiverse theory

well, I guess I AM, but only for the idea of it.
It would be easy to write something off as "possible" and say it would happen in a different dimension.
However, the theory in and of itself is (in my opinion) flawed for various reasons that I won't go into on this thread.

in application to the game world, it's a harmless yet EASY write-off to explain gaps in continuity

"OH, BUT POKEMON COULDNT MEGA EVOLVE IN RUBY AND SAPPHIRE"
"meh, different universe."
Too. easy.