Tobar said:

That post was pretty convincing until the end there. I've seen BB in person, he is no puppet on a stick.

Actually, JJ mentioned a while back the BB-8 was puppeteered on set with digital work done to remove the wires/crew. It may be that either the robotic version wasn't completed till after shooting, or the current robotic version doesn't allow them enough fine control in the movement to accomplish the level detail they seek. How the actual set-up was on set, I'm not entirely sure of.