Something is amiss. It’s about a 15 minute drive from the cruise port to the airport. They will want everyone off the ship by 930 latest. Putting those two things together, it looks like they are implying that the transfer wouldn’t leave until 11:15, which makes no sense.
I have taken ship transfers many many times in Fort Lauderdale. They usually leave between eight and nine, and off and there are several buses spaced out during that time frame. So that would put one at the airport between 8:30 and 9:30, not 11:30. So somewhere the information you are seeing has gotten muddled.
The only reason I know of to take the ship transportation is if you have onboard credit that needs to be used up. You can book the transfer once you were on the ship, and there is no reason to do it ahead of time, so you could straighten out the time issue at guest relations who will advise you which transfer time to book.
or, if the ship transfer is pre-booked for you as part of a pre-paid package, guest relations can advise you as to your transfer options.
as noted, Fort Lauderdale is an easy airport to get to. If you decide not to take a ship’s transfer tgere will be several other easy and inexpensive choices.