I would like to suggest that the reason Xerneas never got pregnant before the MC was since she intimidated most other Pokemon like Maple said Legends do at the start. She's probably how the scientists figured that out too.
That and she would be so rough and forceful that she makes any that get near hear want to just run away from the pain even though there is no chance of death or being permanently hurt only the MC is willing to go through being pounded.
Sorry, should have specified, meant in spite of the pre-existing breeding kink. Mostly just thought the bit about Maple figuring that part out from her would be funny.
