There is a huge difference between being a linguist and being a translator. Linguists formally study various elements of language, not necessarily foreign languages and translation. Like many linguists, I am a linguist but not a translator. Most linguists do not even venture into foreign languages unless they are doing comparative/historical linguistics or finding a unifying theme among syntax and phonology.
From what I can tell, Hoshi Sato is a linguist since she developed the syntactic and phonetic algorithms for the Universal Translator, and apparently neo-Uhura studied xenolinguisitics. But Uhura [prime] didn't do any of this and merely works the Comm system. This doesn't make her a linguist and I have never seen any evidence to suggest that she has any formal linguistics training.