Does this really works? I mean how can this work properly, if a person is asked to pass KYC only after he wins and tries to withdraw his balance. I have never seen a casino sending funds back, because they were transferred from some kind of a "grey" wallet. I have never seen any casino refusing to accept gamblers funds because the origin of the funds is questionable.
I haven't experienced yet and I have never read someone posted this, I think it's make sense since if the casino refunds back the money, the gambler will don't have to say that as his case is already resolved.
Usually it happens when the gambler want to withdraw their profit, the casino will do many investigation toward the accounts. Maybe the casino will reject and refund back the deposit money, if the gambler send a huge amount of money.