scholars can't account for the origination of the phrase Son of Man. It's unique to Christ himself.
Huh? The phrase appears in Ezra, Psalms, Daniel, Ezekiel and many other places, including extra-Biblical sources, usually carrying no indication of divinity. It's not even remotely right to say it's unique to Jesus.
They call it an ideolect, and he only used it when referencing himself. So when Christ asked, who are they saying the son of man is? It was the same as him saying, who are they saying I am?
Jesus was written to have often used the phrase "son of man" in reference to someone other than himself. It's an interesting conflict in the gospels.
son of man is not a phrase found anywhere else at that time, and when he said it it was not a reference to the Old Testament references to someone like A son of man, which is a different phrase.
That is patently untrue.