Murray, there are two separate issues. Intersection of the tail or the prop arc by the rotor which can happen during routine engine starting, beginning of prerotation, etc., is absolutely a problem, and needs to be addressed. RAF had a similar issue at one time.
But the ASRA clearance standard, as written, seems unreasonable, and hard to demonstrate in any event. It doesn't say, "some degree of flapping," it puts it as an absolute. If you flap the blades badly enough to distort their shape, I don't think there's a machine out there that doesn't risk having them hit the keel, the ground, or even the pilot directly.