"They can, yeah, but that doesn't mean that they will." In his experience, people who've lived through something like floods and witnessed other people die aren't always in possession of the best powers of observation they've ever had. "Better to be safe than sorry, anyway."

No, he doesn't have super strength, but the idea of sitting out of the work just because he's not the most muscular person alive isn't something he likes. "Well, 'course they could, and I'm sure they are, but what about the rest of us?"

He probably could find something else that doesn't involve shifting heavy rock, but it's what he wants to do, and he's just a bit stubborn once he gets set on something.