I don't see any evidence TOS/TOS movie Uhura was supposed to be a linguist, in addition to being a communications officer, so the ridiculous scene in TUC isn't really contradicted (though I wish it never appeared!). We do see her repairing her communication station in an episode, so it leads me to believe her skills are more technically oriented. In the army you have signal corps soldiers, and then you have linguists. Two separate fields.
It doesn't mean Uhura wasn't fluent in foreign languages. It just means her specialty and profession as communications officer was centered around a technical field. And really up to that point, what need did we have for a linguist with the "universal translator." That device sort of renders linguistics redundant.
We didn't see a communications officer double as a linguist until Hoshi on Enterprise. In fact, it is implied that her efforts were what helped build the universal translator design that Uhura used.
With Nuhura, I suspect they just carried Hoshi's linguistic role over to her for STID.