Of course, a map will never be the authoritative source of a territory -- hence the saying. But what sets OSM apart from many other mapping projects is its focus on local knowledge and actual people. If people in an area call something by a name, then in OSM, that's its name, even if there's no official name for it, or if nobody really uses the official name.

sometimes people use “authoratative” to mean “what [government] thinks” (e.g. “authorative borders”)

I agree, see my other comment - it's some organisations that have an expectation of OSM that is unreasonable.