The admin of the site isn't claiming this, but rather the fact that OP had various alts with which he had played with, double spending funds when he loses and withdrawing when he wins.
Unless 'Jake' can provide concrete proof that this has happened, I think that it makes more sense for the admin to pay out his dues. I'm fairly sure that there are previous cases of similar nature, I mean that's what happens when you've got 0 confirmation deposits.
Though, this site has been exposed previously as a scam various times, and even though they are still running and may be paying out some users, it doesn't mean that they are safe to use. The fact that they have .1% house edge in the first place is extremely sketchy, as reflected by their bitcointalk reputation.