I'm perturbed. You just funded that. Which means that prior to yesterday, you did not have a cold wallet at all. That also leads me to consider you probably haven't secured the cold wallet properly.
You also claimed to have 4-figures of BTC before, then 3-figures. That cold wallet barely comes to 100 BTC.
I will hold my promise though, and remove the negative trust.
DC, but what's wrong with holding money in fiat? Having a big bankroll is having a big bankroll and if you're worried about how they secured their bitcoin wallet, perhaps they were actually safer when their money was in a traditional bank (FDIC in USA, or whatever equivalent). Anyway, I agree that they should sign a message from the address. Just suggesting that these guys seem to be step-by-step, doing the right thing, and this situation, as it stand now, is much better than things looked a few days ago when everyone assumed they were long gone.
Looking forward to hearing back from yoler that he got he withdrawal.
If this became a standard to hold money in fiat, many sites would start to claim offline funds allowing for higher maximum bets.
BalloonBit did this and then there were many complications because they could not afford to pay out or at least delayed it until they could. This isn't good practice. Sites should be able to access funds and pay right away. Having a transparent cold wallet address provides proof of funds and solvency.