I'm surprised if Livecasino is still want to accept coin from mixer, most casinos usually return back the coin to original address or they will confiscate the funds and terminate the gambler's account. They should be have a reason why they accept it, because they're regulated casino and they need to being honest when the regulation become more strict.
I think that is not about receiving a deposit from mixer but rather the depositor make their platform as a mixer in order to clean the history of the coins deposited on the platform. But just like what the other reply here stated, this can be used as an excuse to prevent players from withdrawing their fund from the platform. But still it is a matter of debate because people who deposit funds in gambling platform to play doesn't mind the wagering requirement because they will meet them eventually while playing on the platform while those who wanted to mix their coins will always find this annoying. (though there are players that wanted to gamble a little then withdraw as soon as they get a good amount of profit)