I'm afraid you're wrong because the GTS lets me offer Flower Paradise Shaymin...
*facepalm* Because that is the shaymin you actually catch ingame? (shaymin is in the flower paradise) Like I said, JP plat gets oaks letter soon, which means JP lv 30 shaymins will be legit now. THAT is the one that will be tradeable. Till then, all the ones are hacked. (as all the ones currently have either classic ribbon, or the letter isn't out yet)
And don't bring up tweaking, that's still not legit. This is exactly what happened when tehy lifted the darkrai ban 3 days before releasing the member card.
And to add about Arceus, they lifted the bans when they release the items. The ban wil still be in effect even after the movie.