*Googles*
Yeah, okay, technically Gamefreak considers them "Mainline" games. I'm wrong (again). I think I get confused because they do tend to keep the "turn-based" games and the "experimental" games separate, whenever they talk about them. Even if they are both "Mainline", they are kept in two different categories, usually.
Then again...I think ALL the official stuff is "canon" one way or another. Pokemon does have a multiverse, after all. Ask Ketchum is out there, somewhere. So, I'm not exactly sure what "Mainline" actually means. Outside of stuff that's of a higher priority than the other spinoffs.
Because...there is NO "Mainline Timeline". Because of the nature of having two versions of each game. And having choices about who the protagonist is. Vaguely speaking, the events all happen. But, the details are different depending on the version. And it's kept really vague about what happened, when events are referenced in other games. It's really more like DC Comic's Hypertime, where the big memorable events happened, but everything else is only kind of vaguely a possibility.
Sometimes simpler is just better in comics.
screenrant.com
The Divine Continuum and how it relates to the greater DCU get explored, but do Batman's parents care about that?
aiptcomics.com
(Very, very minor spoilers for Legends Z-A. Fair warning.) For example, Legends Z-A actually can't really happen in either the X or Y timeline. Because they mention that Team Flare seems to have captured BOTH Xerneas and Yveltal in the past. When originally, it was just one or the other. So, Legends Z-A can only really happen in it's own timeline, where some sort of hypothetical "Z Version" with both Box Legendaries were included was released. Some version of Legends Arceus definitely happened in this timeline, because of the exhibit at the museum. And there's references to a bunch of other regions. But, I don't think we can say that ALL the games happened in the same timeline. If only because of stuff like HGSS and ORAS slightly changing things and repeating events, even outside of the version differences. Specifically, ORAS seems to be "more" canon to Legends Z-A than the original RSE, if only because the Delta Episode gets referenced a few times. Despite both being "Mainline" games. And the fact that ORAS itself kinda-sorta hints at interacting with the original RSE universes via the Link Cable. Thus, we can probably assume we're dealing with some level of multiversal shenanigans.
So, yeah, I'm not actually sure what "Mainline" actually means, at this point. It's not just the games set in the same timeline. It's not sharing the same game mechanics. It's not even really just the games developed by Gamefreak, because BDSP is also a "Mainline" game. I guess it just means "the big tentpole games"? Or maybe just the ones that are compatible with Home? If you can move your Pokemon to a different game, it counts as "Mainline"? Which means Go is a Mainline game too, which feels wrong, but I guess that tracks.
...I'm overthinking this. I know that. But, still.