I don't believe this to be true, unless you're a stowaway deliberately hiding on the ship. They nominally target 10:00 (or later) to begin the boarding process and just check the box that all non-continuing passengers are off the ship prior to that point. It's not like the person on the dock calls HQ and says "hey, @ChiefMateJRKfinally walked off the ship so go ahead and start boarding." Sure, it's somebody's job to make sure that the stragglers are off, but they generally complete this without a problem. I've sat on the ship through a B2B transition, and the last names were called well in advance of the first parades of special Haven passengers (the ones following a crew member waving a "move aside, HAVEN coming through" sign).