>>49419857PLA is a spin-off by its pure definition : it's a derivative work based on specific details from the original games, aka the past. It doesn't mean PLA isn't a primary type of game.
Pokémon Colloseum and XD are also spin-offs, this time focusing on different aspects from the original work. Unless I've missed somewhere proof of them being some dark future of the same universe as the original games, they are part of the secondary type of game, unlike PLA, being a story set in a completely different world with different characters, or as we call it sometimes : a side story.
And in case some faggot decides to seethe and want to use the excuse of a negative emotional bias as to why I don't say they are mainline, I like both PLA and the Colloseum serie but being precise is crucial to get closer to the truth. We don't use words with specific definitions for nothing.