That sort-of makes sense Finman: If they establish a pollen arc and nectar above the brood, then, by placing a box underneath, you are providing space for the queen to continue laying. The problem I see is that the nectar can come in so fast that they don't respect this boundary. They will put the nectar anywhere they can and this can still restrict the queens egg-laying space.
I think most people here would add space above the nest as honey storage. The truth is, of course, they need both. That is why I dedicate the lower two boxes to brood and everything above that (hopefully) to honey. I am not using queen excluders either by the way.