What I do know is that future TOS Spock didn't emerge into the Abramsverse. Simply because TOS Spock well knows that Kirk didn't command the Enterprise until his early thirties. And for him to express surprise that young, barely out of Academy, nuKirk is not already in command of the Enterprise clearly illustrates that the Spock that emerges into the Abramsverse isn't TOS Spock.
Your argument seems to hinge on Spock Prime being able to closely discern Kirk's age. Allow me to echo several other posters here in pointing out that this argument is rather weak. Consider what we actually know about Kirk's age.
In Star Trek
(2009) Kirk is 25.38 years old when he meets Spock Prime, according to the stardates in the film. Correct me if I'm wrong, but we don't actually know exactly when Kirk took command of the original Enterprise. We can make an assumption based upon what we do know, however. We know that the Enterprise is on a five-year mission. We know that during the middle of the second season Kirk is 34 years old ("The Deadly Years"). We know that the five-year mission lasts for at least a year and half beyond that episode (approximately). We don't know when Kirk's birthday is, beyond a stardate in "Where No Man Has Gone Before." Since that stardate is found on a tombstone which gives Kirk the middle initial of "R." and due to the notoriously unreliable nature of stardates on Star Trek
(1966-1969) this information doesn't help us. For all we know Kirk may have just turned 34 prior to "The Deadly Years" or he may have been about to turn 35.
Knowing all this information, we can guess that Kirk is somewhere in his early 30s when he takes command of the Enterprise in the original timeline, probably between 30 and 31.
Therefore, Spock Prime emerges into the past at an indeterminate point (Nero didn't know when he was either, which is why he must ask Robau). He meets Kirk, without a tunic indicating rank, at the age of 25.38 (Kirk may be "barely out of the academy" in the new movie, but keep in mind that due to the death of his father he delayed entry into Starfleet). Spock misjudges the age of his old friend, who he hasn't seen in decades, by five years. Big deal.
But before I continue going off into the deep-end of creepy obsessive fandom, I'll leave it at that.