It’s technically separate from the actual rating code, and so the winrate formula for example might be outdated, compared to the backend code as noted here
Linked there in the glicko pdf is at least the win rate in Glicko, which might need to be adjusted for scale
for glicko2, but it doesn’t include the volatilities.
I don’t actually know what the proper winrate formula would be for two players, taking all variables into account.
I think you can find some examples and tables of winrates with and without handicap in older posts