(After checking nintendo's official VC site linked above)
I really don't understand the logic behind selling GBA games on the wiiu instead of the 3DS, which we all know is more than capable of reproducing them.
But then again, It's probably just the same thing they did with earthbound. Making these highly wanted games (along with snes and n64 games) only available on the wiiu will force people wanting to buy them to get the console.
I guess later on when the console gets better times (or is completely forgotten) they'll make them available on the 3DS too.