Make KYC before customer start betting (if he is a super high staker, or if you see something strange unusal here, this would not apply "normal" players that betting low amounts) and not after he want to cash out winnings!
I dont see why a gambling site would even want to implement this. Its basically like saying, hey gimme your identity or else you wont be able to play in here and why would someone want to give away their identity to an unknown site that he visited for the first time? Its just a bad idea and potentially scaring a first time customer away
Either way, even if most people are now fond with KYC on a crypto casino but the majority would still want to avoid it