Plot hole: When Sam and Dean realise they need to destroy the hook to stop the Hook Man, they find out that it has been reforged into something else. They state it needs to be set on fire to stop him, but if it was melted down and reforged then it has already been set on fire and the Hook Man shouldn't be latched on to it in the first place.
Continuity mistake: When Sam and Dean break into Lori's dorm, Sam notices (and the camera pans towards) an open window. The camera then cuts to Dean. When the camera cuts back to Sam the window is closed. We watch Sam open the window and climb through it.
Continuity mistake: In the very first scene with Lori and Rich kissing in Rich's car, Lori's seatbelt is shown to be over her arm close to her shoulder. The camera cuts to Rich and back and the seatbelt is now behind her arm and lower without her having moved at all.
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.