Last year I just added a PND which worked right away - then wondered myself why I'm allowed to add a new version of this but not modify the info myself. I think currently anyone can replace any PND (the old won't get lost of course).
You're right - seems to be working correctly. As a test I downloaded your opendune pnd, changed the version number and tried to upload it. The page then said:
"WARNING: You are not the maintainer/owner of this application.
You cannot update an application that is not maintained by yourself
Maybe you should contact the maintainer if you have any updates."