We know that Pier or Terminal 2 (North) is the assigned Princess location, but with two ships in port, the other ship is piered up at one of the South Terminal locations. The problem for those driving is that you might leave from one terminal and return to the other making the choice of parking an issue.
If we knew that the ship was leaving and returning to Terminal 2, then no problem - we park at that garage. If she was leaving from 2 and returning to the South Terminal, then maybe we park there and take the shuttle back to 2 after dropping of the luggage. Same with the reverse.
Having done all these combinations before, it really isn't a problem, but it's good to know before hand if necessary.