It’s not a bad strategy: just figuring out what to do can be much harder than getting it done (which can be more easily delegated). Architects (of old) made the big bucks in the days; now according to the google model they’ve all become senior engineers and the definition of and piecing off of work is much less formal (not to mention that it might go out to interns or the community rather the junior devs).

I can also picture it organically happening: if I were a core dev, would I focus on the issues "anyone" could pick up, or the ones that only someone as deeply invested into the code base as me would have any hope of untangling?

Firefox is not their primary product and they have no competition. /S

Oh... I consider Mozilla methodology a good methodology. Staffs probably can do both well and ill defined works better than volunteers, but they do have comparative advantage in ill defined works. A problem with methodology is that well defined works can be delayed, but Mozilla do have massive contributor pool so that it is not usually a problem.