These obviously don't belong to a Constitution Class where the Constitution supposedly is NCC-1700
Quite so, and it's thus a good thing nothing requires us to think they would be Constitution
class. There have been quite a few instances in military history where ships (or aircraft or vehicles) of seemingly identical design have been divided into several classes either because of design origin (some are refits into modern standards, other are modern newbuilds), significant internal differences (one is powered by diesels, the other by gas turbines) or mission differences (where the hardware differences are relatively minor but nevertheless reflect the mission).
I have no objection as such to those ships sporting registries lower than 1700. What I do find objectionable is that those ships use registries from the "Court Martial" wall chart. If we are supposed to believe that the ships on that chart are all "heavy cruisers" or "star ships" or whatever of the various canon identities we assign to the sort of ship Kirk flies, the Trek universe is so much diminished. Not to mention Starfleet is screwed when all its leading ships are undergoing repairs at SB11 simultaneously!
The beauty of this positive Retcon Maneuver:
1) Jefferies Rule has been reconstituted
That would be a massive downside, as it would mean the vast majority of the registries seen elsewhere in Star Trek would have to be changed as well, to correspond to this doubly fictional rule. None of them ever intentionally did, so all existing compliance would be by sheer chance.
3) "Constitution Class" is a colloquialism in the broader sense: If you start with this class, have the next design to be indiscernible from the outside (Enterprise Class), then have a refit transformation beginning with USS Constitution that will also include previous Enterprise Class Starships which then will equally end up as (new) Constitution Class Starships, I wouldn't find fault that the majority of fans refer to these vessels just as "Constitution Class Starships".
That sounds really nice. Of course, it can be extended back and forth in pseudohistory, too: the designation "Constitution
class" could have been slapped somewhat arbitrarily on a certain number of designs associated with the refit history of USS Constitution
, while a large number of similarly shaped ships would be associated with the designation "Irreverence
class" because their refit history was more closely related to that older vessel (say, NCC-1622), and others would be known as the "New Caledonia
class" because they and only they, despite originally having been Constitutions
, would be refitted into an even more futuristic standard spearheaded by the conversion or construction of USS New Caledonia
We don't see futuristic counterparts to Kirk's ship, with mysteriously high registries, on screen. But we do see older counterparts, with mysteriously low ones. So the above sort of fuzziness is probably indeed going on in Starfleet.
We may also treat Starfleet as a realistic organization rather than as a dramatically simplified one. It would be rather natural for such an organization to use several different standards for naming the ships, depending on who is talking and to whom. Going sufficiently far down that path, we could even explain away "STARSHIP CLASS" ultimately... Without having to change a bit of what we saw with our own eyes on screen.