I don't think that swap.btc can be trusted as much as a wallet. It is fine to buy swap.BTC and keep it in your hive-engine wallet, but there is a minimum to withdrawl as bitcoin, so you are better off swapping swap.btc back to swap.hive and keeping the Hive. I would keep BTC in a BTC wallet you control like Exodus. Although I think its smart to have swap.BTC, its just a smart contract iou. Not your keys, not your coins. The Bitcoin is in a wallet that is controlled by the smart contract. You are doing what I think is smart, which is having a little bit of swap.BTC in your Hive account.