--snip--
Does this sound fair for both party?
At least not from the gambling website's end, because if KYC documents have been provided, they need not to harass their customers like this. I'm personally a fan (yes I'm still am) of sportsbet.io but the number of complains being raised on a daily basis have rung alarms in my heart for them.
Even if it's a crypto bookies, you still need KYC to identify a person.
That's absolutely true that KYC can be asked from any entity when and whether they see it to be fit. But even after going through Veriff, an automated verifying service, what makes them not to give the result in OP's favor?