The movie also has Uhura taking over communications because the senior communications officer can't tell the difference between Vulcan and Romulan.
So there's three dialects of a language very close to Romulan. It would be like an American not being able to understand someone from the UK and being replaced by someone who can understand English with Scottish, Irish and Australian accents.
Back in Desert Storm I was with a unit where the radio operator needed another Soldier with him to translate. No biggie right? What he was having trouble with was comms between a Field Artillery unit from Arkansas and the British 1st Armoured Division. Yes, both speak English, but the accents were so thick that it was, at times, very hard to understand.