Yeah, Nintendo of Japan employees don't seem to ever leak these things, even in private untraceable legal deals as we've seen elsewhere. I also think the Japanese people are overall less inclined to steal things, or maybe they just don't get a good chance to do so. A lot of our NFR carts were just stolen by employees of GameStop, etc. If that RS demo never got into private hands, I doubt we'll ever see it.
The beta/proto Ruby, iirc, was another one of those private legal deals with an ex-employee, and the only reason the rom couldn't be publicly shared is that it has some sort of data that could possibly be traced back to the original employee, and in turn could cause him legal trouble. And as I said, Nintendo Japan doesn't leak things like this. Private deals like this are always from Americans and Europeans. That's why I don't think we'll likely see a distro cart for the Old Sea Map either.
Edit: I couldn't find that article I read years ago detailing all about the Ruby beta rom, but apparently it has been released since then.
Edit 2: A note on this DP demo in general. While the ORAS and SM demos have so far been the only widely accessible pokemon demos, the DP demo was playable at kiosks in the US at GameStop, and perhaps other stores. The ORAS and SM demos were exclusively digital 3DS downloads, while the DP demo is a physical cartridge. You can find these leaked carts on eBay just like the distribution carts.
