Onehash does have this kind of feature but it's just an option for the bettors. If you want to register, it's okay but if you don't want to, you have an option to deposit anonymously and you will be given a certain bitcoin address to receive your winning. And after that, the deposit address will be given to you so that's how you bet without any registration. You are not enforcing your gamblers to use it but you are making their lives easier by providing an option.
Even if you make an account on onehash, your identity will not be disclosed. Making as account is always better because in case of any issue/ dispute you have at least an account to take up the matter with support.
The only way the identity can be disclosed is by doing the KYC. Making account will never have any impact.
I'm just giving this kind of feature, a casino won't disclose all of those registered users on their site and it's their duty to protect each user that they have. And what's good with them, they don't require KYC and they are giving you an option to register or not.
Which means, gamble at your most convenient and comfortable way. This is freedom that most of the casino's should have although there's still some perks if a gambler is registered to the casino where he gambles.