True, but Unicode does say that all alpha-2 codes are valid. So while Unicode isn’t saying “this is a list of countries you need flags for”, they do say “go here to find the list of countries you need flags for” - which is mostly a (reasonable) decision to punt political pressure onto somebody else :)

So all that to say: Unicode is still representing language and/or written culture as it is at a point in time (which may be less relevant in the future) - and that’s OK, and absolutely compatible with their aims.