The first and last parts of each name are apparently generated separately, since, for instance, naka (中) combined with shima (島) is pronounced and transcribed nakajima.
Well, it's more rare, but "nakashima" is also used. Ofcourse one can't have any special expectations from a random generator of sorts. Like the translations..."nakajima" doesn't mean center of the island, but rather island in a lake or some other enclosed body of water.