I doubt that any casino will consider crypto earnings as source of funds. Casino will ask for the bank statement at least.
Decentralized exchanges are also like that and any regulated institutions. When you're a whale trader and reached a point where they ask for an enhanced verification, you should never tell that your source of funds are from crypto earnings or else it will just complicate things. As long as you don't have documents verifying your source of funds, they won't believe whatever your story is.
This is an eye opener to me and it is also telling everyone to go look for job that crypto earnings including trading is not a jobe. I think they did so knowing how volitile the crypto is, that anyone could lose everything. Why they consider mining could be that you have your mining equipment which cost much already and you Will continue to mine irrespective of the bear or bull of the market.