This is something that's been bugging/worrying me lately.
![image.png.9e6060472984b664c98f61621e9364df.png](https://projectpokemon.org/home/uploads/monthly_2017_09/image.png.9e6060472984b664c98f61621e9364df.png)
This is a cap Pikachu I genned way before the actual release just to test the Z-Move. It's obviously illegal, but whereas older PKHeX builds properly flagged it that way, the most recent ones are flagging it as legal.