It is possible that the crop as defined in cameras.xml for the high-res mode is not 100% correct. You can adjust the crop manually by enabling the hidden and disabled option plugins/darkroom/rawprepare/allow_editing_crop=false in your darktablerc file, and then use the new crop sliders in the “raw black&white point” module after restart.
Btw, can you reproduce the same w/ the high-res G9 sample from https://raw.pixls.us/?