It seems there is simply no established main thread for cartographer related questions and that causes some sprawl. If a thread per cartographer and interesting submodule were present we'd see much less of a sprawl. The only reason why other popular map/minimap addons do not have this sprawl is because they are well focused on one thread.
Overall traffic on the maps forum is slow. Updates on the first page span 2 months which is pretty long. Yes there are 10 cartographer related threads on the first page, but any other map addon that is in any way active has visible positions. Top 4 positions are all of different map addons.
I'm not sure when compartmentalizing certain addons off from a category makes sense but it doesn't seem crucial to me for maps right now. It's not a lot worse than say unit frames where pittbull and to some extend grid cause some sprawl but I find it not very problematic. It's not like I see active threads literally getting pushed off top positions or even off the first page.