"Generic placeholder" is fine - we have to believe in some of that in TNG Okudagrams, especially as regards shuttle shapes (but also the Potemkin in "Second Chances").
The funny thing about Operation Retrieve is that most of the stuff on those charts is "to (artificial) scale", that is, not "in perspective" - the objects are not to scale with the distances, but OTOH planets don't get smaller if they are on the far side of the star. The Eagle being half the size of the Potemkin there, and the Potemkin being the appropriate size in comparison with the Excelsior, thus works out beautifully in establishing the Eagle as a lesser ship, regardless of whether her silhouette is generic or accurate.
As regards TOS, lesser ships really should include lesser starships. As of 2265, it makes no sense for Starfleet to have retired all starships introduced in 2245 or even 2225 - after all, it makes no sense for Starfleet to retire all the starships of 2265 when 2285 rolls along. The old-timers, yes - Kirk's relic could be from 2225 designwise, and long on the teeth due to the abuse imposed on her by the skipper. But there would always be multiple generations of starships around, the designation even within TOS explicitly applying to ships as old as the Archon.
Trying to insist that a TOS starship must be like Kirk's thus makes little sense. Yet it may further tempt one to think that "starship" and "only a dozen like her" would have some sort of a logical connection, or even equivalence, when nothing of the sort is supported by the show itself...
Timo Saloniemi
The funny thing about Operation Retrieve is that most of the stuff on those charts is "to (artificial) scale", that is, not "in perspective" - the objects are not to scale with the distances, but OTOH planets don't get smaller if they are on the far side of the star. The Eagle being half the size of the Potemkin there, and the Potemkin being the appropriate size in comparison with the Excelsior, thus works out beautifully in establishing the Eagle as a lesser ship, regardless of whether her silhouette is generic or accurate.
As regards TOS, lesser ships really should include lesser starships. As of 2265, it makes no sense for Starfleet to have retired all starships introduced in 2245 or even 2225 - after all, it makes no sense for Starfleet to retire all the starships of 2265 when 2285 rolls along. The old-timers, yes - Kirk's relic could be from 2225 designwise, and long on the teeth due to the abuse imposed on her by the skipper. But there would always be multiple generations of starships around, the designation even within TOS explicitly applying to ships as old as the Archon.
Trying to insist that a TOS starship must be like Kirk's thus makes little sense. Yet it may further tempt one to think that "starship" and "only a dozen like her" would have some sort of a logical connection, or even equivalence, when nothing of the sort is supported by the show itself...
Timo Saloniemi