Yeah the support for BSC network is missing at bet105 and I do hope it will be added soon. They have the support for erc20 and trc20  network but not for the bsc. I don't think anyone will be willing to deposit USDT using erc20. In most cases if you transfer USDT or USDC from the Binance wallet or any other decentralized wallet, the transaction fee is almost nil. This is indeed helpful as you can transfer money to and from the gambling site at a very minimal cost.