This isn't mentioned in the article, since one of the anti-piracy/-emulation techniques I didn't discover at the time of writing it (due to my dump being an overdump) is that many of the games do this. They screw up input so it either boots but you can't play it at all, or input is unplayably slow. It detects it by having an interesting memory mirroring quirk in the cartridges that no other GBA carts have.