Owen

Firefox Focus hides your IP address by default. The Firefox Focus feature hides your browsing activity from your internet service provider (ISP). This is helpful if you are trying to keep your browsing activity private and anonymous. Firefox Focus does not keep your browsing history private.

If you want to keep your browsing history private, you will need to use a different browser.
The main downside to using Firefox Focus is that it is not always reliable. If your internet connection is slow or unstable, Firefox Focus may not work as intended. Additionally, if you want to use Firefox Focus with a VPN, Firefox Focus may not work with certain VPNs.