Benedict Cumberbatch as Smaug Motion Capture B-Roll

Below is a brief video that shows Benedict Cumberbatch performing as Smaug the Dragon from The Hobbit: The Desolation of Smaug. While I can see how his line readings, facial expressions and head movements were translated to the final performance of the pure CGI character, I have to admit I can't figure out why his body as a whole is also sporting the same motion capture dots and how they where used. I guess the upcoming release of the Extended Edition may clear that up.