Then you educate yourself on those versions, and discover that the "dev" edition is not a prerelease version at all, unlike beta and nightly, which are. The Dev edition is a version of the main release channel with flags turned on/off to enable all the "only powerusers need these things" functionality out of the box.
Like installing whatever extension you want directly from file.
I think you're wrong about that. My Firefox Developer Edition install has upgraded itself to 71.0b6. My Firefox install is at 70.0.1. Both claim to be up to date...
Like installing whatever extension you want directly from file.