His music documentaries were just part of a string of Subjects he made films on. He is not a musician.

He presented a lot of good historical material to millions of people. Unfortunately people take the material and decide it is The Correct Version of History.   

Hank Jr. is just the most obvious example, where Burn's taste or desire for a coherent narrative caused him to give him more importance to HWJr than he actually had. I wasn't there in the 30s, I don't know how much of the Burns narrative was the heart of the story. But we were alive in the later parts of the story, and his telling of it during that period is off-kilter to say the least. In the past he's shown poor understanding of early Irish immigration. It wouldn't be a big deal, except generations are going to assume whatever Burns puts in a film is gospel.