“The fact that the Apostolic office grew from the original 12 is also biblical.”
Don’t be so quick to agree. Judas Iscariot was one of the original twelve and the office did not grow out of them but out of the gift to the churches in Ephesians 4 after His resurrection.
Paul was not an apostle? Judas's office was filled, Paul's appointment by Christ added to the number. Ask and you shall receive: the growing Church was in need: He showed us the way, as He always does.