Thanks Bent, I received the 1/8000 sec files. I was going to wait, but I post the thumbnails now so that Peter can better align any processing of the result he gets to these adjustments. To better compare, I converted both files to to gray scale using the monochrome picture control with contrast +3, and pulled contrast slider all the way to the right, and then adjusted exposure so that right edge of the histogram is in the middle. So not quite as extreme contrast adjustment as I showed for the thumbnails earlier. [Edit: For better sensitivity. also increased picture control contrast to +3]
I think it looks very similar among the two D500 bodies, with slightly different patterns, but the pattern persists between exposures within each body (thanks for supplying multiple 1/8000 sec exposure, only showing one here):