Earlier quoted context omitted.
OEM configs have never been enough to implement everything they need in Tor Browser. They eventually started their uplift effort [1], to upstream all the patches and features they've added to it, so that they can possibly just use OEM configs. Project Fusion is a superset of that effort. [1] https://wiki.mozilla.org/Security/Tor_Uplift
Could someone please explain what "OEM configs" means here?
The key config file is distribution.ini. [3]
[1] https://hg.mozilla.org/build/partner-repacks/file
[2] https://www.mozilla.org/en-US/about/partnerships/distributio...
[3] https://brashear.me/blog/2017/12/07/how-to-deploy-firefox-wi...