^I think the reason they dated the movies that way was to reconcile Nimbus III being around for 20 years as of TFF with the Romulans not being re-contacted until 2266 in "Balance of Terror." Although I've never understood why they didn't just round down. I mean, they put TWOK 18 years after "Space Seed" instead of the explicitly stated 15 years, so why not go the other way with the TFF reference?
It would make more sense. I accept the 2285 date for TWOK and TSFS, but prefer to place TVH and TFF in that same year.