Michael, lots of questions. I'll get into them presently, but one thing I see is that you are wanting to think through the reasons why one methodology is superior to another. Unfortunately, you don't have all the information. Here are the papers involved in Jones' testing of the late 1930s and early 1940s. (And they purposely tested negatives derived from a variety of luminance ranges.)
Originally Posted by Michael R 1974
Jones, L.A., Russell, M.E., Minimum Useful Gradient as a Criterion of Photographic Speed, JOSA, vol 25, Dec 1935.
Jones, L.A., The Evaluation of Negative Film Speeds in Terms of Print Quality, Journal of the Franklin Institute, vol 227, n 3, March 1939.
Jones, L.A., The Evaluation of Negative Film Speeds in Terms of Print Quality, conclusion, Journal of the Franklin Institute, April 1939.
Jones, L.A., Nelson, C.N., A Study of Various Sensitometric Criteria of Negative Film Speeds, JOSA, vol 30, n 3, March 1940.
Jones, L.A., Condit, H.R., The Brightness Scale of Exterior Scenes and the Computation of Correct Photographic Exposure, JOSA, vol 31, n 11, November 1941
And in addition to Simple Methods for Approximating the Fractional Gradient Speeds of Photographic Materials is what established the 1960 ASA film speed standard - Nelson's Safety Factors in Camera Exposure.
safety factors in Camera Exposure.pdf