Author intent is never in-universe.
And you're welcome to keep thinking that. Me, I'll let common sense dictate my beliefs, and will go on thinking that Prime Spock is the same guy as TOS Spock, since there's no reason for him not to be, and every reason for him to be.
JJ Abrams, if he exists at all in-universe, is a 21st century filmmaker who is long dead and has nothing to do with the events taking place. But maybe you're right! Maybe instead of asking elder Spock about Khan, young Spock should have had JJ Abrams, the long dead filmmaker on screen to explain Khan. LOL!
You're right! That makes alot of sense!