Mocha and haxchi do what is called signpatches. The wiiu will refuses to run/load any game that doesn't have a valid ticket. So installing the ds vc, will make it faked signed, so you need to run mocha in order to run the ds game. Which means haxchi won't work without signpatches, defeating the point of having it in the first place. When you buy said eshop game, it has a valid ticket, so the wiiu can run it without fakesigning/signpatches.