I believe it's a NO.
Because if a gambler bought bitcoin at any amount, it's still the same. For example, a gambler has 1 bitcoin in his account, and Bitcoin is his cryptocurrency use in gambling, the winnings he is going to receive is also in Bitcoin, to technically it does not affect him, unless he is going to withdraw the Bitcoin in his wallet that he bought @$20,000 for example and the planning to convert it in USDT but the price has dropped to $17,000, then that's a different story.
You are right, it will only affects him if he will going to withdraw it. But as long as it is still in his wallet, there's no problem on it. In terms of the figures, if he has an asset in bitcoin it will be the same but the value will change. Most of the gambler I knew are using doge instead of btc,but it's all depends on the gambler if he really needs to convert it to usdt or fiat.