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.
What the heck are you talking about? Op clearly mentioned that they deemed mining earnings as the only acceptable form of crypto earnings and even shared a screenshot to prove his statement.
It's pretty evident that Stake is in the wrong here which is why they should rectify this issue asap in my opinion.
When I read the OP and the first posts I thought this could be a particular case, or even an attempt to tarnish the name of Stake.com. But it seems that it is their policy. Although it is legitimate that they want to prove the origin of the funds, and the most provable origin is through mining, they should improve their policy and accept different origins, as there must be many people depositing their lawfully earned funds in the platform, and they may be unprotected if they eventually win big.
Not to blame only Stake: as other members stated before, this is a critical point in many custodial platforms, and many people are not aware of it, because almost nobody reads the T&Cs.
Remember that,
not your keys, not your coins.