It's worth noting that different champs have different "Mains Game Share" at different MMR's.
I tried many different interpretations of mains (MMR + Played over X games of champ, MMR + games played at Z rating, MMR + Y champ mastery, MMR + Games with a decay function for when the games were played), etc.
The most consistent one was just champion mastery at 100k+ (which helped, because it was also simpler to implement).
At 100k (compared to something like 50k) players were consistently outperforming 50k players, but hit a plateau of performance, so that's where I put the bar of performance increase for "being a main". It was also a relatively consistent static increase whether Masters+ players were considered or Silver players were considered.
The TLDR of this is mainly that:
- Newer players of the champion tank the winrate about as much as the mains increase it (lower quantity of mains, even if they are performing better relative to ...