While music and intelligence go hand-in-hand at times, this study is doing an assy job of showing it.
Studies have shown that people who are born with natural musical talent tend to be smarter than the average person, but not necessarily smarter in the generalized definition of the word. There are many different kinds of intelligence (i.e. artistic intelligence, musical intelligence, etc., etc.), and if you're testing a population based on just one kind of intelligence, you're skewering the data.
They should redo this test, then offer up a new graph based on whether the students enjoy partaking in an art form, play a musical instrument, as well as any other relevant hobbies. I guarantee you that many of the bands that scored low on this list will score much higher and vice versa.
Like someone said earlier in the thread, you can score off the charts academically and still have tastes in music that aren't considered "intelligent bands." My girlfriend's sister is smart as hell and her favorite bands are Shinedown, Seether, and Breaking Benjamin. Go figure.