Yeah, I guess I could see people coming in with that take. Personally I'll gladly accept a tether to the mothership if they offer the choice.
That said, I regularly get thinkpieces from Mozilla about the open internet, privacy, requests for donation (which I often oblige), etc., in my inbox. They also drop notifications under the address bar and in a "Message from Firefox" bar at the bottom of the new tab page, which I got the impression they had some live control over.
But maybe not, and/or maybe there's a long runway on preparing correspondence by any of these channels for some reason. If anything, I hope that when they do get around to getting some wide-reaching messaging out there, they indicate that they plan on doing the work to shorten the runway on emergency messaging in future.