Neither does the human. Convincing his captor that he needs to get back or he'll die in months can wait until he has some idea of what the yellow man has in mind and whether it'll even matter to him. Besides, this way he gets to imagine in great detail how he'll retaliate when he gets a chance.

He does start storing weight in one of his ironminds. It's not a revenge plot, it's just easier to walk while only weighing two thirds of the usual.