Metawin is a different casino, it prioritizes Web3 technologies. Metawin gives you the option to withdraw up to 19 ETH per day in less than 60 seconds, without any human interaction. When you offer such a service to people, you have to put a good amount of money in your hot wallet. If you don't put, then you won't be able to offer such a high limit.
$4 million dollar is not a huge amount of money for a hot wallet in either way for a popular crypto casino. Stake, the most popular crypto casino lost $41 million to hot wallet. These numbers aren't big numbers for crypto casinos these days.
I believe that it will not be a big problem if the participant receives a withdrawal to his wallet not after 1 minute, but after five. And if need to involve several additional people to make a manual withdrawal, then it will still cost much cheaper than searching for the stolen $4 million.
I do not know how Stake.com withdrawal problem is currently being solved after they were robbed of $41 million, but it would be stupid if they did not learn a lesson.