I have my own code for calculating the win chances. There are probably some bugs here and there so it might not be perfectly accurate in all cases. For example this Yodin match looks like there could be something wrong, so ill investigate that one.

Edit: There are several important attack order effects in round 1 that decide the outcome of that match. In particular the order of your opponent's Orella/Tenyii and which Serpentine Spy that attacks first.

I'm quite confident that its accurate in the majority of matches though.