Is there a difference between Gamecube and Snes?

No

You will have to be more specific on the question.

I'm not a mod so this isn't completely creditable coming from me. But if i assume the question is referring to using something like the "Retro Bit Super Retro Advance" to play fusion on a SNES. I'd say the reason it wouldn't be allowed is because it's not a officially released way to play the game. Something like a Gameboy Player on GC is officially made by nintendo, and is verifiable accurate. Whereas a converter device like this is not so verifiable and is not official.