True, but why not take what Spock said in XI at face value and accept the Kelvin design and aesthetic is a retcon as well?
Because, as I said, there are other elements in the film that don't perfectly fit, unless you interpret them as retconning TOS itself. Once that degree of retconning is occurring, it's better described as a reboot.
Spock's exposition isn't encountered in the film until after the evidence of a reboot is already water under the bridge.
That's not a spoiler, that's speculation.
But whether or not that's the case, I'd say the IDW comic ("The Return of the Archons," among other stories) and Star Trek: The Video Game
to do with the Gorn) have already beat STID to the punch on that score. There's no way the things detailed in those two sources happened in any form in the pre-Nero Prime Universe. (And before you start that 'if it's not on screen, it's not canon', screenwriter Roberto Orci oversaw and collaborated on both projects.)