Your/our best way to deal with this is simply using the duplicate listing thread to report the situation. When I picked up my copies of the Burger King trilogy, I posted the links to both listings & asked which system should keep the listing. Since the games are packaged with 360 colors, they kept the 360 listings and just made a notation in them that the games are dual-system. Currently those are, in fact, the only listings for those games.
Quite simply, there really aren't enough multi-system games like this to really warrant separate categories- especially given that the vast majority of titles would be demo discs for Xbox anyway. At best, I think a separate Xbox demo category might be worthwhile... but I think sorting them based on packaging is also just fine. Basically, if it looks like a 360 demo, then it's a 360 demo, even if it works on OG, and vice-versa.