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.