With those grippers, though? There's a lot of difficulty in making it scrunch up a sock, and a sock does fit. Doing a long sleeve completely unanchored is probably physically possible with extreme care but I see why they mark the robot down as physically unable.
Definitely not trivial but I disagree "impossible". Better to just not use that word and say "too difficult given our grippers". By saying impossible it implies they are limiting their own thinking, not to mention that RL often comes up with pretty interesting solutions.