Has anyone considered the force of the blast? Even from birdshot, how many intruders can withstand the force of being hit , that is stay on their feet, in a close, in-home environment? The goal is to stop the threat, not necessarily kill.
Once the intruder is down, there's the option to rack another round and offer it to them.
The impact of the shot is no harder than the recoil when you fired it. Less, even, due to loss of kinetic energy to the air in between you.
You don't knock people down with the blast of a shotgun... they fall down as a result of their injuries. If you don't actually injure them because you wanted to sting them first and give them an opportunity to ponder their life-decisions, they are not stopped and are still an immediate threat.