Even if you did not hide your username there on Roobet we could not have known that you have won this bet because it is very difficult to trace people from username as people do not keep their real name or forum names on the gambling site.
Yep, but without masking username, technically it cannot be called anonymous, but pseudonymous. Anonymous is when no one can see who places the bets.
Since they serve slots from big licensed companies, I don't think users can be anonymous in the sense of IP/TOR/No-KYC forever. Well, if at the moment we can still withdraw without KYC, we should enjoy it while it lasts.