To me, what you wrote makes no sense at all, because if a certain online casino is blocked in a certain country, then I don't see how using a mirror link would make using the same legal? As someone already wrote, using a VPN to bypass the access ban can only lead to problems in case of any bigger win - because if they ask you (and in most cases they will) KYC you won't be able to withdraw your winnings.
In reality, it’s not. Just like what @xlay mention, we even have a mirror link on bc.game dedicated for PH users through bcgame.ph which PH players can access freely while we are not allowed to play to the main casino same with other casino.
Casino doesn’t declare it publicly but they are using mirror link as loophole to counter their license restrictions to certain countries since the registration is attached to their main website not on mirror link.
Again, they are not officially saying to use mirror link to access their website for restricted users but they leave them accessible to everyone for unknown purpose which we all know what it is.