The whole idea is that most of us love TOS Star Trek and after 45+ years, it's sort of fun to try to explain inconsistencies.
If there are
inconsistencies within the context of TOS, I agree. However, I can't see why "Starship Class" for the original series should constitute (pun) such an inconsistency.
The inconsistencies came when people with the "It's just a TV show" (seriously speaking it is IRL) attitude started to create these inconsistencies, because they wouldn't or couldn't do proper research and/or felt they knew better than the original creators (I call this arrogance)
I dislike any kind of revisionism (maybe reading George Orwell's 1984
didn't do me any good) and disrespect at the expense of the great people that gave us Star Trek.
Nobody is trying to erase a "canonical fact" as you put it, but technically, if the Defiant's plaque in the Enterprise episode "In A Mirror, Darkly" shows Constitution class, well that's canon also!
Are you paying attention to the various "flame" posts in reply to my post? Rather than to explain or rationalize the official "Starship Class" every attempt is made to ridicule it and push it over the cliff on behalf of this "Constitution Class" popularized by Franz Joseph, who took it from Greg Jein (but didn't like Jein's NCC numbering), and who wasn't even involved in the production of the original show and who wasn't even a Star Trek fan by his own admission!
IMHO, "Starship Class" is canon for the TOS Enterprise
and her sister ships where "Constitution Class" for these is a retcon activity whose canon value could be put in question from a strictly TOS point of view.
I don't know why you feel the urge to resort to fecal allusions or try to state I have problems.
I can happily live with the original "Starship Class" mentioned in the The Making of Star Trek
and seen every week on the Enterprise's
bridge (The plague is there in plain sight and we know what's written on it).
So apparently, others do have a problem with that, not me.