I've not any knowledge of Swap Magic, but with the Swap Trick, you put a spring on the button that tells the system the tray is closed, meaning it will tell the system it's still reading a disc.

The system reads the disc in multiple stages. Checking for the country and if it's a real disc comes first. After that's done, put in another disc, and it will read it. Like, it used a real game as a fake I.D.