Lets put aside about the proof of payment from OP but lets focus on the false advertisement by the casino.
The casino put a banner of NO KYC for crypto players, which is something against their own terms where they reserve the right to ask for KYC.
If you are a gambler who are against KYC and you see a banner tells you that the casino is a KYC free for crypto players, you must be very interested to play in the casino.
This is the main problem in this topic IMO, a false advertisement to attract crypto players who want to play anonymously.
Everything needs to be taken into account when we try to analyze the situation, even if the terms are very clear about the casino asserting their right of asking for KYC whenever they want, that is not the way they are promoting their casino, they are falsely advertising they do not require KYC, so any gambler reading that may assume that their terms and conditions will reflect such policy, when in fact this is not the case, making it perfectly obvious the casino itself is engaging on shady practices.
False advertisements can fall under fraud. They are defrauding cryptocurrency player by promising or advertising a no KYC for crypto player banner misleading them into believing that they are exempted of KYC but in fact plan to implement KYC when the winnings are big. Actually, the case is not a matter of whether the casino implements KYC or not, their TOS is void by their advertisement, just like in the earlier reply stated. As far as I know, when it comes to terms and conditions, the current implementation or announcement weighs more than the standard policy.
So @OP shouldn't be asked to submit KYC because he is a crypto user and the platform just promised through their advertising banner that there is no KYC for crypto players.