The Old Mixer wrote:
^He said "in TOS"...but FWIW, I don't think that in TOS, it had even been established that the Enterprise was a "Constitution-class" vessel...the dedication plaque said "Starship Class".
IIRC, there was a discussion a while back here about when "Constitution Class" became a thing in TOS, and it seemed to be a contemporary term with the production of the show, I think even appearing in one of the bibles or draft scripts. I believe it was shown on-screen several times looking at Scotty's technical journals. It may have also been on Khan's screen in SS as well. Despite the "Starship Class" on the plaque, Constitution was still being used at the same time, and interchangeably, and is canonical. Agreed, though, that nobody ever "said" it, in dialog, until later (movies, TNG).