Gamefreak deliberately did not patch in the USUM Pokemon, forcing people to buy the new games to compete. Pretty sure they didn't patch XY to be compatible with ORAS megas but I'm not sure.
Either way as
>>45960001 said GF will squeeze you dry any way they can, and not patching the game is one of many ways.
>>45960190FRLG was compatible because the data of the non hoenn Pokemon were already in the game, that's not the case with SWSH, missing Pokemon are just gone and would need to manually be re added.
>They could very easily release a patch that allows access to Pokémon between gamesThey won't.
