You are requested to leave as soon as you finish breakfast. When you leave your cabin to go to breakfast, you are not supposed to return to your cabin (take your carry off bag to breadfast with you). They hope to have all passengers off the ship by 9 am. That having been said, we were on one cruise where Customs hadn't cleared the ship until late, and the doors weren't open to start disembarking until 9 am! The early seating people weren't happy with that wait.
Usually, by the time early seating finishes breakfast, people are leaving the ship. IN that case, the "everyone ashore" is 9 am.