Discovered accidently when testing update of tags, not really a problem for me, but surprising (Version 12.7.0.0).
Seems also to be independent of flag -overwrite_original.
I did not test other OS.
Haven't found this in FAQ.
Cactus
This is mentioned here (https://exiftool.org/exiftool_pod.html#WRITING-READ-ONLY-FILES).
- Phil