Thanks for your comments, guys!
To get a proper understanding... So someone has bought "Super Mario Advance 3 - Yoshi's Island (USA)" in Nintendo's VC shop (or whatever it is called :p) and then extracted a part of the file which is the actual GBA ROM?
Well, I still think the game should go to a WiiU related dat because even in a different form it was released on the WiiU... Are there any similar cases (maybe also on other consoles) which would be comparable?
That's what's happening. It could
make sense to fit into the Wii U, but you can also download the installable files for the full vc package (think wads for Wii) which would more likely end up in the Wii U DLC section which ends up raising confusion. The issue is that some of the roms (GBA, NES, maybe others) end up getting modified by Nintendo or otherwise before being put up onto the eShop, which is why the .gba roms have ended up in the gba section. In addition to this, there's at least two new
gba roms coming out of the Wii U vc, Game & Watch Gallery 4 (JPN), and Drilldozer (EU) which were never a thing before.