In my experience, it takes about 45 minutes to an hour to clear whatever they have to clear and then begin disembarking. Then they disembark those with shore excursions first - this can be a bit time consuming if you're tendering in. But I wonder when they say 6:30am if that's really when the ship arrives or if it arrived during the night - in which case maybe they'll be all clear and start disembarking right at 6:30am!