I think it is just a default time and I wouldn't pay too much attention to it. They have buses running from MCO to the port pretty regularly. When you arrive and are greeted by the RCI people they will likely put you on a bus fairly quickly.
When I arrived at MCO a couple years ago the RCI transport desk asked if I'd wait for another flight to arrive, but if not they'd "burn a bus" and transport me and a few others right then and there. Everyone else had agreed to wait so I did too. As it was we only had to wait about 20 minutes until that flight arrived.
Similarly, on debarkation day I was in the diamond member express departure and was sitting in the bus at 7am.