I’m not sure Firefox even uses favicons anymore but that definitely isn’t navigation so it isn’t blocked.

It does, not sure why you would think it doesn't? I do know chrome gets annoying about them, always requesting a sites favicon even when it doesn't have one listed in the document.

I haven’t seen them in the UI while I remember them being shown quite prominently. I wouldn’t really expect them to be used only for sites added to favorites because that’s a privacy issue.

Might be a setting in yours, or a plugin of some sort?

Your tabs don't show the favicon?

Note that it said "top level" navigation.