Why is it necessary according to the rules to do duplicate races at Night? There is no unlock or bonus related to doing that, it's only a visual change within the race itself.
How? Again, the layout isn't different at all nor is there anything locked behind doing them.
100% means completing everything that is tracked by the game and/or gives you an award, not doing everything. You don't do Green Hill in Sonic Adventure 2 as part of the 100% run because it doesn't give you anything, only thing that's relevant to progression is getting all 180 Emblems. Similarly in a more casual sense, you wouldn't consider walking into every single building in an open-world game like GTA or Spider-Man to be required for completion...
I would have to agree that 100% would include doing the night races too due to them being a different event. I am also not sure if there is a physical in-game tracker for completion % and don't think just getting something or not is enough to say it's not tracked by the game
If I remember correctly saves in main menu only show your trophies and maybe how many platinums you've gotten.
