Continuity mistake: Gary (disguised as Sam) sits at the bar and orders a banana daiquiri. The woman next to him tries to engage him in a conversation as he sips his drink, and each time the camera switches between him and the woman, the level of his drink changes noticeably up and down.
Other mistake: When Dean is listening to Sam's voice mails that he left while in Gary's body, the voice in the recordings are of Sam. If Sam was in Gary's body, they would have been of Gary's voice.
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.