Pete, Guido: while I understand your "if it ain't broke, don't fix it" feelings, here's how I look at all the "rules" that are coming down: (are two colons allowed in one sentence?) there are more and more measurers entering the hobby. As more people participate in an activity, more clarification is needed.
I have found the same as Guido, that my differences in calibration tapings are less than ¾". BUT, when we get emails asking about tolerance for this, that, and the other thing (from new measurers), that is an indication that a clarification is needed.
Ideally, we would have a more-complete manual that answered questions before they are asked. That would enlarge the manual considerably, though, and would require much of someone's time. If we add items as they arise, we are clarifying items that are not clear enough for newbies. Remember, many of us have many courses under our belts (not that I wear a belt while measuring). Newbies don't have the benefit of our experience. If we can help them by putting clarifications in the manual, why not clarify?