Pokémon Legality

[Mr.Terax]

This is a mistake by PKHeX

Some Mega Stones and Attacks mark Pokémon as illegal, because Mega Stones are unreleased and Attacks are invalid.

But that's not right

[ReignOfComputer]

If the Mega Stone was released recently, it's already been updated in the code (see recent updates on GitHub).

For Attacks, some elaboration or further details would be nice.