Just a few observations on the logic here, not on SHB, as I have too little experience with that.
Just because you still see a lot of SHB does not mean you aren't interfering with their life cycle. As mentioned they fly long distances and they may be coming from somewhere else. It still seems like it's a good idea, as much as it's not a lot of trouble and it's not an insecticide, to interfere with their reproduction.
Just because someone in the South has never seen them pupate in the hive does not mean that someone in the North hasn't. The SHB behavior could vary a lot according to the climate or temperatures at the time.