Really? I don't remember that. I think the PB and banana would probably be good, if, as the author said, it's very cold. Maybe just a bit of chocolate. But I think not added in the blender. Instead, make little chips, and stir them in once it's done. DARK chocolate, like the little chips they use in mint chip ice cream.
But if I said that, it would have been because I don't like PB and jelly, as a combination. Never did. And what would be the liquid part of the smoothie??