I see your point,
but in my head (maybe its wrong
) Im thinking that thicker diff olil will provide more stress to the drive train.Try to drive a car with locked diffs.Take a 2dw car under ekstreme acceleration only one wheel will "burne"slip ,if the diff has a thin or no diff oil.Off course you loose traction, and there will be less stress on the drive train?? I think the same goes for a 4wd car.So my conclusion less traction less stress.
But again I not racing just bashing.And my conclusion might be wrong
.