It was illegal at one point for Jews to acknowledge Jesus as the Christ and so He challenged a believing Jew to confess Him as the Son of Man. If that meant the same as Christ then Jesus would have been encouraging the man to break the law. Obviously the way John records it, that wasn’t the case. Jesus was avoiding the tricky question of being the Christ and focusing on the equally important matter of Him being the Son of Man and being believed to be such, and being believed in as such. John 9. So the fact that Jesus is the Son of Man is not quite the same as Him being the Christ. I believe it is about His preexistence. As seen by Daniel, Enoch, Esdras. The man had already been punished for confessing Jesus as the Christ, so this was different. More than Christ, Son of Man.
