So hear me out.
While Koraidon and Miraidon are not Paradox Pokemon in the game, I think it's similar to how Solgaleo and Luanala are no longer UBs. I still think the reason for them to look the way they are is due to a paradox.

Koraidon only looks the way it does (ballsack wheels) because its what happened to a Miraidon that was forced far back in the past, changing to fit its new environment better.
Conversely, Maraidon only exists because Koriadon was forced to adapt to a far future it shouldn't have existed in.