Has it been "officially" declared now that "Yes, Wolverine's claws can cut the Hulk's skin"? Before, the "official" line that while the claws were sharp/hard enough, Logan just didn't have the psychical strength to use them to cut the Hulk.
Of course, the Hulk Family presumably wouldn't have as strong skin as their father/grandfather/whatever. And this is Logan cutting from the inside out.