It could be explained also by Section 31, if they had further enhanced his genetics.
It's an alternate universe from the get go, even before the Kelvin incident. That's one easy way to solve everyone's issues with canon. The Abramsverse is one of endless multiverses (like the ones hinted at in TNG's Parallels). Easy solution.
They can do what they like. It doesn't matter if Khan is white, or Vulcan is destroyed, or Chekov is born earlier. Alternate timeline.