If you want to directly swap BTC, there are much older services like:
These REPUTABLE exchange sources you mention give the correct exchange rate.
Whereas all of these brand new pop-up exchanges like btcswap claim to offer an amazing exchange rate to encourage as many deposits as possible.
People usually find these unheard of exchanges while reading a tutorial that promises 30%+ profits in just 15mins by swapping BTC --> ETH on the site then going to a reputable exchange and swapping ETH back to BTC.
I've seen so many of these recently. It's one of the biggest scams going around in the crypto space at the moment. As soon as anyone follows one of these tutorials and deposits to the unheard of exchange they will lose their money. It's an atomic swap arbitrage scam and it must be earning the scammers money because there are so many of them about.
Sadly, these asshole scammers are targeting people who want to get rich quick because often common sense goes out of the window if you have this mindset.
The reality is, there is no easy way to get-rich-quick online. No exchange is going to give it's users a massive exchange rate just for the hell of it.
I hope this prevents people from losing their precious Bitcoin to these scammers who have no morals.