King Daniel wrote:
"Starship class" is set dressing. It's never been said in such a way as to mean class and not type. "Constitution-class" is canonical,
That's silly. Both appeared on the shows and both are canonical. If it isn't a "big deal", why weigh in?
Edit: Why it's silly: You are picking which class you consider is "canonical" and so is Bob and other posters. Pot and kettle and all that stuff.
Surely what's spoken carries more weight than illegible background screen graphics and the like? I'm not entirely sure about TOS, but during TNG/DS9/VOY/ENT the art department and the writers didn't have the best communication - hence bizarro nonsense like Voyager having two warp cores and two computer cores on it's MSD, which were explictly contradicted in dialogue.
And besides, new canon overwrites old canon, and new canon is decided by whoever rules the franchise. That's how it works - so Picard's "Constitution-class" in TNG's "Naked Now" and "Relics" overwrites anything contrary in TOS, just as "James T. Kirk" overwrote "James R. Kirk" 45 years ago.