Nope we can't say automatically that they are cheaters if they said no on a KYC procedure since there are people that doesn't like to submit any vital information online since maybe they are afraid for their personal security and we can understand that since there's huge risk if we hand it to anyone.
But since a reputable casino ask this then maybe people should consider to trust them or if they really have trust issues and can't really trust those platforms that ask a KYC even if they had long years of good service and reputable in this business then maybe playing in those casino who ask KYC is not for them. Then maybe they should think about to stop participating on any online gambling activities since most likely KYC will be ask there.
This is right but we can't remove the possibility that they are cheaters since most of crypto users are already aware of the KYC process because regulation is already entered in our crypto world. Players should stop using any form of centralized services if they don't want to undergo KYC process because every business with a license usually has a potential KYC procedure.
Most of the cheaters use this argument against the casino to hide their identity once caught because a normal user with trap funds in a casino especially a huge amount will have no problem doing KYC unless the casino specifies in their ToS that there's no KYC even in the future.