With three prominent ships, two of these all-new, the movie made Starfleet more diverse than ever - and now we're supposed to believe that the Grissom doesn't represent diversity after all, and that "Federation Survey Vessel" is just a fancy name for a retired starship?
Well, it's apparently not without historic precedent:
MENDEZ: Inspection tour of a cadet vessel. Old Class J starship. One of the baffle plates ruptured.
I don't believe that the Oberth Class is the only survey vessel the Federation has at its disposal, certainly there are current designs created just to perform this task but possibly with less armament than Grissom
(as a former starship or cruiser) might have had and therefore was picked for this delicate mission.
And apparently with a enough firepower to make Kirk concerned, wondering whether Esteban would open fire upon Enterprise
On the other hand I find it somewhat unrealistic that we hardly (almost never) saw the introduction of new designs but in ST III "suddenly" witness two brand-new Federation designs. To assume one of these had been (unseen) in service before would add a little more realism, IMHO.
You may (and will) believe what you want. If my treatise ensures that Trekkers, that feel the ship to be an older design, will not be greeted with a "Picard facepalm maneuver" in the future, I have accomplished what I foremost intended.
I think you are reading too much into this.
Isn't that a hoot...
...yes, it is.
I won't exclude the possibility I'm reading too much into this, but my observations (on which the theory is based) are laid out and you are free to like or dislike, discuss or ignore these.