>>20690349>>20690398G/S/C added Special Defense, and there was no required block from R/B.
IV's is one simple mechanic that can easily be adjusted through the transfer. It's not something GameFreak would be afraid of doing. Raichu and Scolipede, for example, had their stats changed in X/Y. Does that mean we have to block transfers?
As for "muh uniqueness", I'm sure that GameFreak could come up with other non-game-changing ways to make each one feel different from the rest.
Oh wait, they're stagnating their creativity with megas.