Hi grumpy, there appears to be different schools of thought on backlapping between grinds...I am in agreement with you...
Most greenkeepers I know have professional machines that are hydraulically driven and have a 'reverse' feature that send the reel spinning backwards at a given speed.
They use 120 grit emery and oil paste to achieve the desired result and judicious use of the 'bedknife buddy'
They have explained that is just for 'touch-up' only for (as you have said) very small tolerances.
