the bulletin explains that some 172Cups were being failed as the testers were confusing the set-up with the ABS equipped cars - the Cup's got a sprung load-sensing compensator block above the rear axle. then it goes on to mention that some vehicles are just engineered with very little rear brake effort (as in this case). i've not had any bother with my tester, but you could see if that document satisfies them
it's also worth taking the car out for a blast and giving the brakes a hard time before they retest it, as the calipers can become lazy due to the lack of work
ed. typing as Fred commented