I'm not sure why would you put "protect" in scare quotes here. This protection against fingerprinting is very real. Having any installed fonts that didn't come with the OS (and that includes fonts that are installed by other programs), makes your computer a lot more easy to fingerprint and track. Not everybody is interested in this protection, but this protection is very real.

It also doesn't seem to be enabled by default, since it tends to break some sites, as explained above. If you want to disable prevent Firefox from doing that, just don't set "Enhanced Tracking Protection" to Strict. You can even go for full Custom mode and enable "Protection from Suspected Fingerprinters" (which blocks some fonts as described by GP) only for private windows.