Except of course, it renders Nimoy's cameo and the entire time travel aspect of the movie pointless.
Except Nimoy has already played a Spock from an alternate reality, the Mirror Universe. If he can be a Spock from one universe, why not another? And the time travel is just a way to say "everything you know is wrong". It's pushing a reset button while not overwriting what's gone before. (or not. For all we know the old universe was overwritten. We didn't see anything of it after Spock and Nero went through the black hole.)