As far as I know China not allow online gambling although I don't have source news. Since bitcoin isn't traceable if don't know who own the address perhaps China people's would use VPN. And I believe most of legit crypto-currency gambling doesn't ask for KYC. So China player can get benefits of it.
Yeah I think China dont allow online gambling casino on their country instead the Chinese are scattered the world and building casinos in other countries and mostly Asian countries such as Philippines,Thailand Singapore and Malaysia and there are lots of them that I cant mentioned since they are so many to be mentioned
But the question is does this happen in China?or in some parts of he world