The results here are based on the data of every game played each day starting 9/13/2021.
The Elo ratings are calculated using the following:
Elo ratings for the unwinnable games are set to zero.
Elo ratings for the winnable games are set to the variant defaults.
Elo ratings for the players are set to 1500.
When a game with zero Elo points is lost, nothing is done.
Otherwise, an exchange of points is calculated and takes place.
If a game with zero Elo points is won, its Elo rating is first set to the variant default.
The daily files are in simple CSV format and processed locally first to generate the results you can find here.
It's important to have reasonable default Elo values for each variant such that the value doesn't change much and stays at the same value. Check out the "Variants" tab and "Diff/Plays" column in particular.