That's really interesting! I don't know quite what to make of it. I believe there is a lot of data behind the notion that an overall course drop as in Boston does provide a measurable advantage (Bob B, Ken Y, others please comment?).
I haven't run Boston in a long time, but I did feel that the downhill was helpful and the hills not as awful as feared. Maybe someone needs to do a study that goes beyond the top ten (?).