Two related items from Henry. On page 184 he states "Kodak actually recommends a safety factor of an overexposure of 1/2 to 1 stop. When measuring exposure from a neutral gray card (18% reflectance, RD 0.745) Kodak recommends increasing the indicated exposure by 1/2 stop." Now I haven't read the two Kodak publications he references, I did notice he doesn't have any of the papers by Connelly in the bibliography. I'm a little surprised that all the effort with exposure meters, he never seems to have worked out the relationship between C and K. Also on page 145 he talks about the 0.10 speed point being 4 stops below Zone V (meter reading).
Maybe this is comes from trying to balance the popular terminology with the scientific information. Maybe he didn't read the papers on exposure. There is a reference to Stimson's An Interpretation of Current Exposure Meter Technology, but not Connelly's Calibration Levels of Films and Exposure Devices which was critical to my understanding of exposure. Maybe exposure theory isn't an interest of Henry's.