Good proxy for contact rich vs pick and place tasks. many simple robotics tasks (pick and place, stuff astra is good at) can be done with a really stiff controller and no real interaction with world

4. A stiff controller can hide engine differences, a softer one exposes them. Pushing blocks through a narrow channel, our stiff controller kept the hand within about 6 mm of its path in all four engines. With softer gains, peak deviation reached 16–28 mm in three engines, under 1 mm in Genesis.