I'm pretty sure they have more than just 5 games. I know there is a Chinese only Super Mario 64, yet it doesn't show up on the DS Release roster.

The DS is called an iQue in China, and only Chinese DS can run the retail Chinese DS games (Not sure if pirating works). It has something to do with the Chinese DS Firmware being the only DS with the chinese characters on it.

I can only guess that maybe this has some reason or another to do with the fact that we don't see many Chinese exclusive DS games here.