It seems that at least at one stage PUBLISHER was proposed to be added to the Ogg Vorbis Comments section of a file, and that it should take precedence over ORGANISATION if it existed.
ORGANIZATION
The organization responsible for producing the album; i.e., the record label.
PUBLISHER
The organization responsible for publishing the album. This is often the same as ORGANIZATION. If this is the case, both should be given to allow for searching by PUBLISHER and CATALOGNUMBER, but if PUBLISHER is missing, it should be assumed to be the same as ORGANIZATION.
https://web.archive.org/web/20120429102447/http://reallylongword.org/vorbiscomment/I found that in a quick search. I have no idea if the proposals were adopted.
I'm sure someone (David?) could find a more up to date and official reference.But if the proposals were adopted, it would make sense for MC to read the PUBLISHER tag and put it into the [Publisher] field, and if the PUBLISHER tag didn't exist, but the ORGANISATION tag did, then the ORGANISATION tag should be put into the [Publisher] field.
Of course, you could then debate whether MC should have both fields in the Library (it doesn't have [Organisation]), and whether it should write both tags, and how they get related. But the above would seem to meet requirements without breaking anything...
...Well, it would be annoying if a file was imported with a PUBLISHER tag, which was written to the [Publisher] field, which then got modified and written to the ORGANISATION tag, and then the file was re-imported (forgetting Sidecar files for now) or imported into a new Library, so that the old PUBLISHER tag was used instead of the updated ORGANISATION tag. But that is tagging for you. Always a compromise, and always different opinions. Not much really in the way of internally and externally consistent standards.
PS: It isn't possible to add a [PUBLISHER] field to MC to see if MC would import the tag from the file, as MC already has a [Publisher] field, so any attempt to add the field results in it being automatically renamed "PUBLISHER (1)". Nor is it possible to edit the existing [Publisher] field to make it [PUBLISHER].