Race-to-idle only means that it's often more efficient to run a processor designed for a given speed at that speed, complete the task sooner, and then power it

Race-to-idle only means that it's often more efficient to run a processor designed for a given speed at that speed, complete the task sooner, and then power it down than to run it slower. That's because modern high-speed processors waste a lot of power via leakage just by being turned on. I think it's often still more efficient to design a slower, lower-power processor in the first place, and most modern phones have such processor cores.