I'm not 100% certain, but that would make me believe that they are having some special itineraries for the first few sailings on Liberty. These will not be the standard sailings.
Mary Lou Scanlon
NCL Pride of America April 24, 2010
NCL Epic February 12, 2011
RCCL Allure of the Seas - September 18, 2011
Celebrity Eclipse - February 11, 2012:
RCCL Navigator OTS - February 9, 2013