I'm 98% sure with banding creature, the only thing that changes is that the defending player assigns the dmg as opposed to the attacking player.
So in a normal situation,
rokapoke could assign all of his dmg to a blocking creature, leaving none of it to trample over to
Mooseman. So if you substitute
Mooseman for
rokapoke, he has the same options.
But like I said, it's only good if you can take care of the Armor or creature in time. If you can't, yeah, you might as well concede and get on with the next game
It's a great play and shows the "brokeness" of this type of card in this format
Same with Black Vise, Sudden Impact, Maro, etc.