Under your theory, there would be no need for this forum (for quick exchange of accurate, reliable info relating to the dir-655) since everything is searchable in Google. That flies in the face of logic and reason.
Well, there is a lot of junk info out there in Google in case you didn't notice.
In fact, I did do a Google search prior to posting and the information seemed equivocal at best. I did find another thread relating to the dir-825 with a similar issue but no one ever explained why closing (instead of stealthing) these ports was considered safe from a security standpoint, let alone the factual basis for making such an assertion.
Now, I've tested a lot of routers, and the dir-655 is the only one of those tested that failed this test. Is there a particular reason why D-link has this port closed but not stealthed, like other manufacturers?
If you have found reliable info in Google that answers these questions, please post a link to it.