what I don't understand in these discussions is why it's considered weird or impossible for Spock to choose to be with Uhura, assuming he was betrothed to some vulcan lady like any vulcan kid would, when really canon has already proved that sometimes vulcans ditch the whole betrothal thing in favor of choosing someonelse.
I mean, hello T'Pring herself ditched Spock for Stonn and consequently Stonn, a full blooded vulcan unlike Spock, chose to be with a woman that was promised to another vulcan and I don't remember that it was considered scandalous or unvulcan.
Why you act like this is somehow forbidden in their society? It's not.
Probably even if Spock was betrothed maybe it was a no issue for him because he did think he'd get spared of the whole pon farr thing so maybe he simply believed that when the time was right he could delete the contract that his parents had made when he was a kid and make Uhura his bondmate with the vulcan equivalent of a wedding.
Honestly, I think that the whole betrothal thing serves the purpose to have a backup plan for pon farr in case people hadn't found a partner on their own.
From this perspective it makes sense, in a way, and it doesn't go against IDIC and free will because they aways have the option to undo these programmed unions and choose who they want.