Christmas Eve has a lot riding on it. Dinner, gifts, maybe church, maybe a movie. The meal can't drag into the evening or everything after it slides. A timed sequence from serve to cleanup keeps dinner tight so the rest of the night actually happens.
Christmas Eve dinner is supposed to be the warm-up, not the headliner. But a meal that starts late or stretches long eats into everything after it. Gift wrapping gets rushed. Bedtime slides. The kids are wired. The evening you pictured dissolves into cleanup at 10 PM. A tighter sequence gets you out of the kitchen and into the living room before the night slips away.
Decide when you need to be done eating, not when you'll start cooking. Ready Time subtracts each step from that endpoint. If dinner needs to be cleared by 7 so gifts happen at 7:30, you know exactly when prep starts, when the main goes in, and when to plate. The evening stays intact because you planned from the end of dinner, not the start.