Yes, some ask depending on the amount you win, if the money is very huge they'll feel you're trying to launder money with their platforms and request for it, although it's true that some use it as a market strateg, knowing fully well that lots of gamblers would prefer casinos that offers privacy to one's that would require them to expose their important documents online. Just that some gamblers don't read TOS to see where casinos that claim to be KYC free specify that they have the right to change their policy if need be.
It's not like this.
Laundering money is when you deposit your money and withdraw it without playing or limited bets. If you bet normally, bet a lot and later win big, it's not money laundering but perhaps casino will try to investigate whether you cheat their casino. If no cheating found, they will pay you for your big wins, it's only possible issues of how you bet and win, and it's not related to your fund deposited to their casino.
Generally, KYC card can be used by many casinos but in different ways, some will write it clearly in ToS as mandatory KYC for better AML, some will not write it in ToS or write it vaguely and they can pull the KYC card against users when they don't want to pay you or see that your account has suspicious activities.