Inconsistent behavior when writing 'Rating' tag

[lokatz]

Couldn't find this in the FAQ, but I encountered some behavior I find somewhat puzzling.  Am writing Rating info to files, in this case a Sony .ARW raw file.  The original file contains Rating info in the Makernotes, like this:

Code Select Expand

[Sony]          Rating                          : 0

After writing new Rating info via -Rating=3, the pertaining fields looks like this:

Code Select Expand

[XMP-xmp]       Rating                          : 3
[Sony]          Rating                          : 3

However, upon deleting the tag again by writing -Rating=, I get this:

Code Select Expand

[Sony]          Rating                          : 3

In other words, the XMP tag was properly added and removed, but the Makernote one seems to have changed permanently.  [This is under Windows 10, with ExifTool 12.15.]
Is this intended behavior?  How can I reset the Sony tag to 0?

Appreciate any suggestions you may have.  Thanks!

[Phil Harvey]

Individual makernote tags may not be deleted.

From Note 2 of the -TAG[+-^]=[VALUE] section of the application documentation:

2) In general, MakerNotes tags are considered "Permanent", and may be edited but not created or deleted individually. This avoids many potential problems, including the inevitable compatibility problems with OEM software which may be very inflexible about the information it expects to find in the maker notes.

Use -sony:rating=0 to reset it to zero.

- Phil

[lokatz]

Thanks!