I wouldn't be quick to call it a "mistake." They're
inspired by the movie and probably not meant to be the exact same thing. That's for the prop experts like Richard Coyle. However, they serve the same function -- lighting while protecting from rain -- and cost less.
I'm a fan myself, but there's a certain point you reach (like wanting a 100% accurate replica of something only seen in the hands of background extras) where it gets to be a little much.
