Remember that “average Joe” is not actually signals only focus, it’s average journalist/ whistleblower/protestor living under a hostile government that may target them and their associates for what the rest of us “average joes” might consider basic free speech.
So a scenario might be, people use signal in Iran to arrange a mass protest on a specific day, word gets out and some of the organizers are arrested and pressured to give up their companions… They cooperate by unlocking phones, but police have no idea who the lead organizer “RndoUsr.40” is and the people arrested never met face to face so no amount of pressure would get them the organizers real ID
And yeah, for us average joes it’s good for aquaintences and because names are easier to remember so it’s handy.
It is on f-droid too. This isnt being “unhinged” its just calling out google for their hypocrisy and pointless "privacy” policies and citing lots of examples.