Why would one column (column A) attach reference frames to an external object and another (column B) attach them to the body? It could be as simple as where the inputs to the column come from. If column A gets sensory input from an object, such as sensations from a finger touching a cup, it will automatically create a reference frame anchored to the object. If column B gets input from the body, such as neurons that detect the joint angles of the limbs, it will automatically create a reference frame anchored to the body.
