And Then There Were None - S6-E16
Revealing mistake: Samuel is very much dead, laid out on the table in the canning factory employee lounge, but as Sam stands over him, talking about whether or not it was right to gank him, you can see Samuel's chest rising and falling as he breathes. (00:26:30)
Revealing mistake: As Dean digs into the dead guy's guts and discovers the claw the pale dead guy blinks.
Revealing mistake: When the woman is under the bed with her baby her arm is covered in blood, but when she touches the baby's face and clothes, no blood comes off onto the baby.
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.