I agree with you, straight KYC after registration is sure far better and easier than having to go through KYC after one have won a significant amount of money and wants to withdraw, but the casino insist that the customer must pass kyc verification before his or her withdrawal will be processed.
I think thats valid to some point. Going through the KYC (Know Your Customer) process during registration can save you the hassle of doing it later when you win at a casino. The verification process may be smoother at this moment compared to a future scenario where you're forced to complete KYC. Even though it's a good idea to get verified early, you should be cautious about sharing your personal information during registration. Not all online casinos can be trusted. That's why it's crucial to choose reputable casinos and not just any you come across on the internet.
If I'm a small-scale gambler who uses a small amount of money to gamble every now and then and barely manage to win anything significant, I wouldn't like to do that. The reason for that is that maybe they don't ask me for KYC verification at all since I'm not making any large deposits or withdrawals, and most of the platforms don't always ask for KYC verification for relatively low deposits and withdrawals and KYC is only triggered if the amount is high.
So, as long as there isn't a need for it, it's better to keep it simply and stay private while you can. However, if I know that I'm going to be spending a lot of money, and I know that the platform is trusted, I wouldn't mind going through it first just to make sure that I won't have any troubles in the future.