I have often wondered about this as well and had read the description on Wikipedia but found it lacking, but I guess that's as much as there is to the story. MIA has lots of odd concourse layout design choices (I'm thinking also of the train to the end of concourse E).

Various parts of the airport give the sense that perhaps at some point it had more functionality than it does now (like maybe allowing international transits without clearing US customs, which would have been particularly useful back in the days when Europe-Latin America nonstops were less common than they are now), but apparently that wasn't the case, and that seemingly all of these strange design choices were just to help people avoid walking to the ends of concourses which are actually pretty short walks by modern international airport standards.