>>55389498 (continued)I suppose this 2019 part of the leak would be a bit more speculation.
If the hacker or his friends still had a back door into Nintendo servers (credentials Nintendo didn't reset or a remote desktop connection maliciously placed on a computer during the intrusion) the friend group could have still been accessing newer builds of the game and keeping up with internal development documents.
May 23rd would have been two weeks before E3, at which point Gamefreak would have had to have committed to not having all Pokemon in the game. Be it an internal document or a newer build removing any reference to National Dex Pokémon, someone in the hacking group could have figured out what it meant and decided to leak it (and considering the autism, perhaps thinking it would cause Nintendo to change their mind or something)