Absolutely right. He could very well be a citizen of Canada by birth, but US law doesn’t consider that. He is a US citizen born abroad of one US citizen parent and one alien parent, both married, and the US citizen parent having lived in the US at least five years after age 14.
End of story. The debate will begin anew over the phrase “native born.” However, he still qualifies.
He is a naturalized citizen. He does not.