I am old enough to remember the days when greens were not cut every day, not even in the prime of the golf season. I can even remember greens with daisies growing on them. Even now in the prime season some courses do not necessarily cut every day, the greens may be driven over but there's not much cutting going on, circumstances can dictate.
7-8-9-10-11 or whatever stimp they may be when cut and initially speed/stimp tested they won't be that for long - drying out, footfall, sun/shade, wind, rain etc etc. And some greens change character and thus speed at different rates to others - exposed greens, shaded greens and the like. Plus slopes on some greens may be okay at higher speeds but on others on the same course the ball will be rolling away from pin areas so the overall average speed will be dictated by the green with the most puttable mix of contour/roll-off/pin positions etc. Also how accurate are the speed readings, not the stimp process, we know that, but how many greens are being stimped to give an accurate initial daily average reading or is it the same area of the same green each time and always on the green nearest the sheds. And green speeds can be quickened up not just by h-o-c but by the use of green rollers etc.
Lots of generalisations, lots of variables. What works for some may not for others.
Atb