Other mistake: Even when you beat both Shiva and Deadshot they're shown on TV monitors at Joker's meeting in the penthouse suite of the Royal Hotel.
More mistakes in Batman: Arkham Origins
Batman: Garfield Lynns, a.k.a. Firefly. Burns on 90 percent of his body. Hmm. His obsession is going to be his end.
Alfred: How unlike anyone I know.
Question: How does Copperhead know Joker took over Black Mask's mob?