Presumably because there have been no other media added. When more are, you will see more than 3 on that page. I had loads on mine as I hadn't viewed most of them. Now I have viewed some and clicked on Mark Viewed for the rest, my page is now empty.
I agree with this part. It would be silly to show old ones. New Media is only for New Media only. (i think maybe he was a little confused and thought by viewing the thumbnail it would be marked as "viewed"
About the Flag:
I think the flag idea is awesome idea. I think it would look nice and it would be easier to see which media is new.
This flag would be extremely helpful on the main media page. (when clicking on the media tab)
Because at the moment you cannot see which ones are new unless you click on the New Media Link
I remember asking to add something similar on xenresources.
I don't see where adding redundancies is helpful. Main page Media tab shows the number of New items. Clicking Media takes you to the main Media page where you can select New Media which will open a page with all new and unviewed media.
Simple the menu is all the visual clues one needs for any new content.
Seems to me this would be better suited for an add on rather than core.