Peter says the criteria was to have walked with Jesus since his Baptism, so what you state is ***what some say*** not what Jesus or Peter says...
I don’t recall the precise wording of that verse. Do you have it handy?
I’m not sure it’s a remotely critical issue. It appears abundantly to me and to much of the Universal Church of Christ abroad in the world that
Paul was an exceedingly important and fine Apostle of Jesus The Christ . . . whom Christ went to great lengths to recruit and transform into such.