I've always felt the timeline was altered way back before Nero arrived; why else would all the characters look different?
But they don't
look different in-story. Spock Prime recognizes Kirk and Scotty on sight
. They look different to us because they're being played by different actors. Just like Saavik looked different in TSFS than she did in TWOK. But within the imaginary universe that we're seeing a dramatized representation of, they're supposed to look the same. (Another example: in "Metamorphosis," Kirk and McCoy felt that Cochrane's face looked familiar, but Glenn Corbett looks nothing like James Cromwell. Ditto in TNG: "Bloodlines" -- Picard recognizes DaiMon Bok instantly even though he's played by Lee Arenberg instead of Frank Corsentino.)