Bob, are you really referring to the Cert form, or the Measurement Data sheet? I don't see a need for the info on a cert, but it would be a better way to phrase it on the data sheet. Better than "difference between shortest and longest" measurements.
When doing cal courses, my taping is usually within ½" for a 1,000' course.
Why is 1.2" over 1,000' needlessly restrictive? That is about ¼-click. Since most people who round Jones clicks do so to the half-click, 1.2" is less than a rounding unit. But, if we allow longer difference in two cal course tapings, it becomes material to the measurement. Granted, half of a click is still only about 1.75", but that is 9" per mile, and 20' per marathon. That becomes material.