He may not be asking for nothing, at least not in the sense it seems to me at the moment that you mean. He seems to be saying something to the effect of: we'll both show our cards at once and if we've got inconsistent upper and lower boundaries, I'm walking.
Given that:
"The typical approach is for both sides to demand something unreasonable—but not let on that they consider it unreasonable—and then negotiate a “compromise” in the hopes that you will end up closer to your side than the midpoint."
He can be seen to be cutting out the negotiating part. They're not going to offer $0 because they expect him to be asking for a fair bit. Saying 'this is the minimum I'll accept and I'm not going to discuss anything lower' is quite a hard bargaining position for the other person to match under most conditions.
If he were actually interested in asking for nothing he'd undercut their offer if it were higher than his minimum, and keep insisting on being paid as little as possible. But he doesn't seem to have done that. Whatever he's done he's not actually talked them into letting him pay for the meal, so to speak - and I can't imagine that doing so would have been particularly hard.
Given that:
"The typical approach is for both sides to demand something unreasonable—but not let on that they consider it unreasonable—and then negotiate a “compromise” in the hopes that you will end up closer to your side than the midpoint."
He can be seen to be cutting out the negotiating part. They're not going to offer $0 because they expect him to be asking for a fair bit. Saying 'this is the minimum I'll accept and I'm not going to discuss anything lower' is quite a hard bargaining position for the other person to match under most conditions.
If he were actually interested in asking for nothing he'd undercut their offer if it were higher than his minimum, and keep insisting on being paid as little as possible. But he doesn't seem to have done that. Whatever he's done he's not actually talked them into letting him pay for the meal, so to speak - and I can't imagine that doing so would have been particularly hard.