Stone is studying the chart and then turns to his intercom wherein he directs repairs crews (or whatever) to switch from the Intrepid
to the Enterprise.
Put together it supports the idea the chart refers to ships being maintainanced and/or repaired and not ships being constructed.
At the time 17 series ships might well have been considered the same as the Enterprise
(this is long before the Constellation
being shown onscreen). It could also be that the Republic
(1371) mentioned onscreen wasn't originally intended as an Enterprise
sister ship. Certainly the Valiant
mentioned later in "A Taste Of Armageddon" likely mightn't have been intended as a 17 series ship given it was fifty years older. But as that list of proposed names started circulating they all might not of remembered what numbers (if any) were intended for which ships other than the Enterprise,
of course. The appearance of the Constellation's
1017 is the wrench in the works that causes all the confusion. We're it not for that it would have all remained pretty straightforward.
Making the Constellation
an older ship upgraded to 17 series configuration is a fair enough rationalization, but there really is no reason why the Republic
has to be an upgrade as well because we never got to see that ship and at the time it was referenced it might not have been intended as a 17 series vessel. And I think Stone's chart was a cheap and creative bit of world-building to establish that Starfleet had a variety of ship classes besides the Enterprise
type. The show couldn't afford to physically show other ship classes, but that chart was a clever non-verbal way to establish that other classes did exist in the TOS universe.
In all of TOS only three ship's registry numbers are seen or heard: 1701, 1371 and 1017. Two of them are definitely sister ships and one might be. The question: is 1017 an aberration or a precedent? I think that comes down to interpretation. Even if you add into the mix the sister ships we've actually seen we don't see or hear their registry numbers except, again, for 1017. And so beyond the Constellation
the only ship we know are definitely sister ships are those we've actually seen. Any other names on any list are mostly conjecture if they weren't mentioned onscreen.
Now there is the question of whether there were any proposed registry numbers in script drafts that didn't make it onscreen and to which ships those numbers were intended. Still, unless those numbers were meant for a ship actually seen onscreen then there is no reason to assume they're sister ships of the Enterprise.
In my opinion FJ was closer to getting it right then Jein even if he didn't put as much speculation into it.