Yes, I would be happy if the audiobook was simply not listed.
So I removed the 'audio/mpeg' stuff and just left the attached change.
I have also deleted the driveinfo.calibre and metadata.calibre files from the device (I should probably have done this earlier).
Now the book list is correct - but the audiobook still appears (with a path that is not quite correct).
If nobody objects, I would submit the modification soon.