There was a play about 15 years ago with Ed Harris playing his American interrogator. Not a good play but interesting. I was very good friends with the late Werner Klemperer. He told me that his father had nothing good to say about Furtwangler. I'm just repeating this - I know nothing about the real story.
Not surprising - Klemperer was a great conductor and suffered greatly because of the Nazis. But, yes, Furtwangler underwent a denatizification procedure and was cleared, and was frequently used for broadcasts by RIAS (Radio in the American Sector).