They would be wrong, unless you are also saying that Jesus was both the Son of God, and Fully God (I know I don’t fully understand it, myself. I don’t think we as humans were supposed to..)!
He may mean that we all pray to the same God as in God the Father of Jesus. Example Jews, Muslims, Christians all believe in the God of Abraham, Moses, Creator of Adam. The other just don’t believe that it was Jesus there all along.