The Objective Intent Test puts McKittrick in a "catch 22": To convince Embry that he is promising, he needs to say "Go ahead, you're all right. Get your men out, and don't let that worry you" in a context in which a reasonable person would interpret the words as promise of continued employment.
But once he does that, he cannot deny that he promised. Under the Objective Intent Test, a person's words and actions constitute a promise to do (or not to do) something if a reasonable person would, in the circumstances interpret them as a promise to do (or not do) that thing.