I can only assume they're referencing the recent hack and subsequent leak of data from Game Freak, including the code for several Pokémon games and some absolutely wild in-universe lore seemingly written by Game Freak employees.
Any fandom in a nutshell when something gets scrapped, some actor says something they believe or feel, when something leaks but never made it to the actual material, when they find a fanfic... Doesn't matter, they want their fetish to be real so they force their head-canon as if it was a real thing.
After reading the scrapped lore one can see why it was scrapped, but idiots will yell it must be canon because they like it.
Nothing against head-canons if they treat them as such, the moment they force them, that's when it's a big no.