>>532416202
>>532416414
You're correct and incorrect at the time because of Nasu shenanigans.
While the multiverse notion already existed in the VNs, with the Lost Belts and Ordeal Call they introduced the idea of a main timeline, pruned/incorrect timelines quantum time locks.
The main timeline being the FGO one, and anything outside of it being a fork or branch.
So FSN, Extra, FSR, etc, are merely spin offs and the main canon timeline that actually decides the fate of humanity is the FGO timeline.