It’s always a case to case basis when it comes to casino account KYC. I still have my account unverified on BC until now even though I deposited huge amount before and do a lot of withdrawals.
But I do encounter casino ask KYC immediately after few deposits and withdrawal so this KYC thingy is solely based on the casino security preference because they can trigger it anytime. I think they are using the casino activity most of the time for the KYC.
But some casino indeed using it to delay or potentially forfeit the big wins especially if they have suspicions that the account original owner is from restricted country since they knew if users use VPN to hide their IP.
Casino or centralized exchange, if people want to use it for a long time, it's better to complete KYC before sending your big fund to account on a casino or a centralized exchange. It's mainly because with more eyes from governments and their authorities on cryptocurrency industry and companies operate in this field, they will create more regulations that are surely stricter with time. So casinos and centralized exchanges will have less choices or even no choice than adjust their Terms of Service to KYC mandatory on all users.
Now things are strict in the USA. and Europe but soon it will spread globally and KYC mandatory will become a new standard in cryptocurrency and casinos that accept cryptocurrency.