Deeper meaning
My guess at the deeper meaning is this: Armless Boy's lack of arms represents his powerlessness, not being able to manipulate the things sticking out of his Happy Gift Box of Goodness. But when someone else does it for him, they are destroyed by big, nasty, black, hairy hands of woe. Perhaps AB always knew, in the back of his mind, the contents of the box and refrained from opening it for that reason. Perhaps he really has arms, but has sucked them into his body cavity because he enjoys watching others getting smacked down by the Big Nasty Hand. Perhaps AB observes with detached amusement as others walk into his Armful People Trap. Perhaps AB is more sinister than I thought...