I'm pretty sure LibreWolf just uses default fonts and ignores the ones installed on your system. It's a measure against tracking. A website can make your browser render different fonts and then e.g. read out the size of the text block and then, depending on whether you have the font installed or not, that size will be different (because the actual font characters will have a slightly different size from the missing character symbol or from characters from other fonts) and they can use that to see what fonts are installed on your system, which can be used to track you.
LibreWolf
Welcome to the official community for LibreWolf.
LibreWolf is designed to increase protection against tracking and fingerprinting techniques, while also including a few security improvements. LibreWolf also aims to remove all the telemetry, data collection and annoyances, as well as disabling anti-freedom features like DRM. If you have any question please visit our FAQ first: https://librewolf.net/docs/faq/
To learn more or to download the browser visit the website: https://librewolf.net/
If you want to contribute head over to our Codeberg: https://codeberg.org/librewolf
Is there a way to change this behaviour?
Don't think so. I think it's part of Firefox's advanced tracking protection and you can only turn that off completely but that would defeat the whole point of using LibreWolf. You could search up if there's a way to explicitely add fonts to LibreWolf/Firefox but I don't expect there to be one.