This is what i expect gamblers to know that the gambling platforms cannot bend down to the gambler's request except if such comply to their terms and conditions, there's no way i will be using a platform but yet insisted that i don't know much about them, if i don't then they are smart enough to fish out things that they know am unaware of concerning to them and then they use it against me untill further proof and informations were given.
Casinos who will do such thing are shady. Because if the platform is trustworthy, they will not use a trick to take advantage their gamblers for something that they're not aware of. It's a common practice for casinos to ask for verification if you win a decent amount especially if you exceeds the limit.
However, this rule should be written on their ToS and they're transparent regarding this.
And even kyc is not compulsory at first for new player, they will understand that this is inevitable in the future. So it's the responsibility of the gambler to read the rules to be certain that they understand and agree on the casino's rules.
In my own personal experience, KYC was not compulsary until I made larger and larger deposits and withdrawals from the casino. Especially if you do, deposit then withdraw within a short period of time more often. We can't blame the casino if they check on their users to find out if they're merely using the site as a sort of mixer/tumbler. But if the user is an honest person who merely wants to gamble, then just comply and there's nothing to worry about.