So it makes more sense that in those instances Stake is more strict on their requirements compared to the verification a small gambler needs to pass.
KYC verification for higher level gamblers makes sense for obvious reasons, but asking op to provide his source of funds doesn't really make much sense. Deeming mining as the only legal source of crypto income makes things worse.
Nope, Stake didn’t mention that only mining is acceptable as source fund in crypto. They just do site an example for this case but anything that can have valid proof is ok with them for example trading. He can request for notarized document for his trading history as source of his fund his trading volume is sufficient to tally on the original deposit that he made on the casino account. OP is just making this issue worst by assuming that Stakes on accepts mining as source of income in crypto.