The Keeper wrote:
The Prime Universe Original Series had a character named "John Harrison" who was NOT Khan. He was just John, a background character seen a couple times going about his routine duty.
They're not just gonna pick some random background character to be the villain. And they're especially not going to go to great lengths to hide his identity if that were the case.
The one thing the original post likely has right is that "John Harrison" has got to be a cover of sorts. It'd be funny if it weren't though.