Evidence wouldn’t be as concrete as source code, but there was plenty of evidence from data miners. Gamefreak kept moving goal posts when it came to why it wasn’t feasible for Sword and Shield to have all the Pokémon which is my frustration with that situation. I think they complained about the capacity of the cartridge the games were stored on was one, which was readily proven wrong. Dont quote me on that. But I do think that was ultimately the case.