Continuity mistake: During the scene when Sam and Dean enter the abandoned shipping warehouse to save Charlie, you can see Charlie's legs crossed while sitting in one shot, but in the next shot they are uncrossed. (00:27:10)
Revealing mistake: Dean borrows Charlie's phone to call Sam. On the phone, the lock screen can be seen, showing that he never entered in any number.
Answer: Angel blades come from angels. It's their angelic magic that makes it special. Therefore, an archangel blade is made magical with the powers of an archangel. They couldn't have just created one or used one, as none of them are archangels.