Not true, FF comes with few binary blobs which are removed from Librewolf. Also there are some things disabled entirely at build time, so they are removed from being an option. So it’s not just the settings, and it’s not plain re-branding. Some distros has gotten it wrong, believing that it’s just a matter of settings, but at least on the case of Librewolf and the Tor browser that’s not the case.
That hey depend on FF continuous development to exist is true, that doesn’t mean they just rebrand.