Sadly, what they "stand for" and what they actually do are two different things. This is exactly the kind of centralization that a company supporting a "free and open internet" (to use their words) should be against
on principle, let alone pushing in their only product of note.
This should not be possible.
Worse, had they not taken the paternalistic, nanny-like stance that you can't even disable the signing checks, I could roll out a script that would make this a non-issue for my users. But no, thanks Mozilla for ruining my Monday.
Might not be the most substantive comment I could possibly make in the circumstances, but I'm pissed. The only appropriate response feels like a string of infuriated profanity directed at their incompetence and decision-making.