Shimano Dura-Ace 9000 Road Brake Caliper
The new dual pivot design makes the section of the arm between the pivot and the pad much shorter, which translates to 20% more power with better modulation. The biggest change is power from the hoods is much closer to power from the drops.
He says half the power improvement comes from the new calipers and half from the new levers and use of the new coated cables.
The small arm attached to the cable-side brake pad (top) was an articulating linkage that added force. In fact, it does add movement to that brake arm, but the design is simply to balance it’s range of motion with the other one for even braking on both sides. The set screw is to adjust that arm’s position relative to the rim.