Canterbury - are you sure that is not just a way of your employer extending the servicing intervals on the aircraft by claiming it is not flying when it is rotors turning on the ground?
You may not be airborne but the engine is still having to turn the gearbox which is still dragging the blades around plus the TR drive and any other ancillaries.
The manufacturers will have calculated the fatigue spectrum of the aircraft and I am pretty sure they would agree that rotors turning on the ground is still fatiguing the aircraft.
Crab,
(without entering the general fray of this thread, but to clarify this specific point) it is entirely normal to only log airborne time in the tech log, and this is the time used for service intervals and component life compliance. Aircraft with HUMS will record this for you. The OEMs will agree that time on the ground running is fatiguing, but this is factored into their limits based on experience (of typical usage).