>>49320403>BD/SPRemakes are their own category. Also, because GameFreak say it's mainline doesn't make it mainline. If tomorrow they say it's an isekai game because of time travel, you would still follow the actual definition of isekai and time travel and call it a time travel story. Same here, it's the first game we have of this serie, if no other come out, it's a spin-off.
"A spin-off is [...] any narrative work, derived from already existing works that focus on more details and different aspects from the original work", here we focus on the past of a specific generation, the 4th one. By definition, the story itself is a spin-off, and only if they were to create more game would it become its own serie of game and thus could be called "mainline".
