They are obviously assuming the engine knock sensor will detect the chain vibrations as early ping/knock and retard the ignition timing. Personally, I think the chance of that happening are remote.
The knock sensor is acoustically tuned to the engine, is mounted on the block (which is pretty isolated from that little chain dragging on the road) and the knock detection is timed to ignition pulses by the computer specifically to ensure that other noises from the engine aren't missinterpreted as knock.
