...that if you lose T/R thrust at a hover or at slow airspeed and start spinning, you don't have a quick, easy, and therefore likely way of getting the engine torque off the the rotor, and therefore stopping the spin. Period. Twist-grip throttles on the collective, on the other hand, offer a readily available means of "splitting the needles" and therefore stopping the spin. That is the key to successful handling of this particular emergency, instead of spinning around until you lose control by disorientation and/or g-forces and slamming the aircraft into the ground...which is exactly what you see in the videos of this LA accident.