Not sure why the time in Nassau was so short, either. However, the ship probably had to stop there because of the Jones Act. I think that essentially states that round trip cruises departing from a US Port must make a stop in "a nearby foreign port." St. Thomas and St. Maarten I think are part of the US Virgin Islands, so I'm not sure if either of those stops would satisfy that requirement.
2007 - Majesty of the Seas (Bahamas)
2009 - Enchantment of the Seas (Western Caribbean)
2010 - Freedom of the Seas (Western Caribbean)
2013 - Golden Princess (Alaska, roundtrip from Seattle)