Yep. He's barring an open-tuned guit. Didn't watch the vid, so don't know what key they're in. I've seen a few players barre open tunings this way.
EDIT: just watched the vid. He seems to be in either open G or open Em tuning. From what these old eyes can make out, he's barring the 7th fret when Joe's playing a D chord, which means open G tuning...I seem to recall that Mick Jagger plays thumb-barred open tuning on some songs live...