Is Mozilla telling the truth when they say Firefox 48 and newer will not allow you to override required extension signing?

Is Mozilla telling the truth when they say Firefox 48 and newer will not allow you to override required extension signing, or is that developer lies? The preference xpinstall.signatures.required set to false no longer works. I tried adding 2 scripts here:

https://winaero.com/blog/disable-add-on-signature-enforcement-in-firefox-49-and-above/

This method did not work and reset my browser to its default settings, which caused me to need to reconfigure it.

I heard you can take the source code, remove the extensions from the signed types file, and recompile the source code to disable the frustrating required extension signing, but how do we do this? You could also just use an unbranded build.