^ As I remember correctly because I don't have enough knowledge on technical stuff on BTC transactions. The 3 confirmations consider as safe and can not be reversed but this is only for small transactions like $1k below. However, in large transactions like millions of dollars in BTC amount will need six confirmation, this is the standard for most transactions to be considered secure. It would be love to use a gambling site that offer for free withdrawal fee and I hope all of them are generous enough to have that free fees upon withdrawal.
I would like to know how many gamblers in the crypto operate with amounts of millions of dollars. In my opinion, there are very few of them and they are unlikely to be anonymous, since if the casino makes transactions of several million dollars without knowing the information about the client, it can be accused of money laundering.