That is rediculous whoever said that.
If you test it at idle, it will give you a reading for idle only. you need to get a reading across the entire throttle range with a load on the motor, not just rev the motor and measure. It is best done on a dyno because the motor needs the load to give accurate readings. HUGE difference in running 1/2 throttle and not moving vs riding at 1/2 throttle down the road. Think about it, how much gas does the motor use if you twist the throttle in neutral? How much when riding? Way more. So you need the rolling/load measurements to mean anything at all.
