I think that's what causes people to not like this KYC because it is too abrupt in asking users to complete KYC at the end of the game instead of at the beginning of the game, of course that is definitely not liked by many gamblers because maybe they don't want their identity to be known just because of a small bet.

But this is not the fault of the gambling platforms, they are being considerate first by not asking for KYC for a start which is their own way of attacking gamblers and requesting for KYC the moment they started and wanted to make some certain functions which is their own second way of retaining the gamblers to their platforms, now it's upto us to be able to present to them the evide of what they demanded or not.
No matter how we want to look at it, it's not right to say one thing in the beginning and do another thing at last; that's a shedy thing that most gamblers usually do. It's always right for you to update and tell the people that this is what they are going to face in the casino they want to start gambling with. Let me know and decide if they want it or not.
Telling someone there will be no KYC of any kind, and you having that in mind before you made your first deposit and you started gambling with them only for you to have a large winning, that's when they start asking for KYC documents. Such behaviour doesn't look okay to me; it's like forcing someone to do what they planned on doing in the first place.
You're right, i will also like to add this as a piece of an advise to gamblers to make sure that they have every possible required information needed for KYC before they started with them because when the time comes for the verification of KYC, some don't even have the proof of every informations required from them, not even access to the contact number or email address used can they be able to provide, which is not right enough from our own side.