Logged to my account to check about their altcoin withdrawal fees, they are friendly with altcoins as far as I can see. They do not mention the fee for some altcoins such as EOS and USDT (I assume it is free)...
Back in 2019 when they still had a presence on this forum, their campaign manager introduced BetHash as an EOS gaming platform. It was powered and built on the EOS network. Lets assume that was and still is the casino's main asset and everything else was added later and has a secondary importance to them. That could also be why you aren't charged fees for EOS but they never cared about adjusting bitcoin fees to an acceptable rate.