In most cases, even trade exchanges place conditions on users to provide passport data in the first place precisely when the user wants to withdraw a sufficiently large amount of funds. Gambling books should be guided in the same way, because not all gamblers deal with big wins.
That's what I am saying that the rules of kyc should be uniform and should not vary with the withdrawal amounts. If a sportbook or gambling site want to implement kyc they should implement it right at the time of making an account on that site and not at the time of withdrawal.
I have heard one or two cases of people who always had this KYC issue at withdrawal and I still find it very strange because the few sites I have visited with KYC requirement always did that at registration and most time I back out immediately because I am not called for such shit . I believe those who have issues with withdrawing probably didnt go through the T&C OF THE SITE BEFORE REGISTERING, IT MUST HAVE been stated that there might be possibility of asking for personal details at withdrawal and if theres nothing of such, that means the site is a scam site
In my opinion, KYC on its own its scam to a decentralized system, I feel its not supposed to be at all by no standard. Well, I feel sorry for bettors still dropping their details on such sites and I hope it wont be released to third parties.
If you are a high roller or a gambler that tends to spend huge amount of money on online casino site, you really should understand the TOS of every site that you want to play with.
Otherwise, it is your own fault when the time comes for withdrawal and other things that the site may require your personal details.
It might not be an initial requirement but later on they might ask those details when you fall to the category of their kyc protocol.