>>43419753It's only not canon to the games in the sense that's it's a separate universe with its own plot.
But the game and anime universes are otherwise near identical to each other. How Pokemon battles work and what Pokemon are capable of is the same in both universes. It's not a "fanfic" because Game Freak themselves are heavily involved with the anime by communicating and working closely with the studio and giving them reference material so they know what the fuck they're doing and don't just make shit up.