Here's another option: committees reach the final list of admits one at a time in an order that doesn't track "definiteness." For instance, maybe Harvard knows they want 2 ethics people, 2 metaphysics people, and one epistemology person in their incoming cohort, and they decide on admissions for each of these areas in turn. So they decide on 2 epistemology people to accept (expecting one to turn them down), then go on to think about their ethics and metaphysics people. But before the whole process is done, the POI contacts one of those epistemology people. So here, we have a good explanation for why someone would be notified before everyone else that doesn't entail that if you haven't been contacted by now, you must be a worse candidate than that person who was notified.