
I doubt Nurse Chapel would have been so actively pursuing Spock if he and Uhura were involved, and in Amok Time he would have sought out Uhura's comfort. And it was pretty clear in Plato's Stepchildren that by season 3 Uhura was admiring Kirk from afar.
Considering that Spock apparently was in a teaching role at the academy his relationship with a cadet was not professional and should have violated ethics standards, so was not particularly believable. Weakens his moral high ground in the Maru incident. That and Uhura at different times had interest in Kirk and Scotty - do they have to hook her up with everyone? One could say that the timeline was different and Spock and Uhura only hooked up in the new one but it's a bit of a stretch since there's no obvious reason the loss of one starship would change academy romantic hookups much.
A sine curve goes off to infinity, or at least the end of the blackboard. -- Prof. Steiner