Watching Star Trek 2009 and I came to the realization that the USS Kelvin (see below) looks very much like a 'reboot' starship (by 'reboot', I refer to the design of starships in the Abrams reboot series which differs from that of TOS). Now I understand that the basis of this series is that it is that Nero's entrance resulted in the formation of an alternate timeline. Logically, however, the events of the alternate timeline did not initiate until after this point though (ie approximately after the birth of James T Kirk). Hence the events prior to Nero's emergence from the black hole occurred as they did in the (original) TOS timeline.
As the Kelvin was obviously commissioned and designed before this, however (i.e. it was designed and commissioned in the original TOS timeline), why would it look like a 'reboot' ship? Surely it should have looked much more like a ship that would have come out of the uninterrupted timeline like the Antares Class or Constellation Class (both of which seem to have been created before the Constellation according to Memory Alpha).
I am of course looking for an in-universe answer; the answer 'Abrams' will not suffice ;)
NOTE: I am not asking why the other ships look different, as with an alternate timeline and the presence of Nero causing new events it is reasonable to assume the difference in design can be explained by different starship designs/designers (perhaps even slight derivations of technologies - consider the difference in the deflector dishes) being employed. I am asking why ships prior to the alternate timeline being created looked like 'reboot' ships.