The S-76A uses a slight reduction in rotor rpm to gain single engine climb rate. The 96% Nr is worth about 75 feet per minute climb increase when the engine is temperature limited. The use of 96% rotor in effect creates the need for a new structural envelope, and could even call for a new Vne chart and the whole structural qualification (in addition to the full 100 to 107% rpm envelope already provided). Since the lower rpm is only useful for establishing single engine climbout, we conveniently controlled it by limiting to flight below best rate of climb speed (one can argue that if you can accelerate above Vy you don't need the lower rpm anyway). This way we give a convenient way to have our cake and eat it too.