especially when you consider that one of FF's target user bases are people who turn off all telemetry

Yeah, though telemetry wouldn't help since this level of attention to UI design doesn't (practically ) exist, and it's unrealistic to expect it from FF, so the next best thing is allow user configuration.

Also you can even have a dynamic sorting section part within some menu based on how often you use a given menu item or depending on which profile you're using etc.

A couple percent of Firefox's user base turn off telemetry. That is a target group, but they're hardly representative.

(I'm not bullshitting. I worked for Mozilla for 25 years, including in the Netscape era. Brendan Eich and I built the Mozilla 1.0 roadmap. I was a co-creator of Firefox along with Blake and Ben. I was Firefox's PM at Mozilla when we deployed telemetry and I was a Firefox and A11Y PM when me and Andre Natal introduced local LLM-based language translation to Firefox a couple years ago (Nightly only, release came last year after I left.) If those credentials aren't enough to make my claim believable, then I don't know what else to say.)

It's definitely believable, defaults are very powerful (I'd expect a higher number, but not a very big one)

Though out of curiosity - if someone turns all telemetry off, how would you know of this use to count?