This explanation is ridiculous. Even if you use the example of David, that makes it worse. David was born later than his brothers (meaning lower) then he was later declared firstborn. So the analogy is that Jesus was born lower than the angels and later (after his resurrection) was declared firstborn of new creation. Colosians 1 is one of the most powerful argument for the unitarian s when you understand that Paul was referring to the new age creation after the resurrection of Christ.