Indeed, still there after one disables all the modules possible and switches demosaic to passthrough as well:
unprocessed_raw dump to PGM/TIFF from the LibRaw package also does not show them…
However, reading in Python using tifffile does show some non-zero data there as well.
I now also see LinearizationTable in this file - could it be that RawSpeed is passing the entire buffer through the table which makes these pixels more visible, while dcraw/LibRaw only applies it to the active area? @LebedevRI
Also, Software : Dotphoton Raw 20210916 indicates this has undergone another proprietary lossy compression scheme, so no wonder shadows are different to the original CR3. And we also don’t know if and what that proprietary compression scheme did to those black areas.