I’d like to add some comments about the rating system of the European Go Federation. This is different from the OGS ratings system.
The EGF uses a rating system defined by 1d EGF = 2100 rating and 1 rank = 100 rating points. So 7d EGF = 2700 rating and 10k = 1100 rating. This is different from the OGS rating system.
The EGF rating system also doesn’t use a 400-rule or 800-rule.
The EGF’s winrate prediction is a customized form of normal Elo rating systems as used in chess.
Here you see the modified predicted winrated vs observed winrate from the FIDE data, that was discussed/proposed by the author of that article:
For comparison, the predicted winrates and observed winrates from the EGF data (these curves are horizontally mirrored and centered around the target rating to which the curve applies):
