Having once discharged a 12ga shotgun, loaded with #6 birdshot, inside my house - I can give direct observation that it worked perfectly.
While most of the errant pellets did penetrate two interior plaster/wood lath partition walls, they ended up lodged inside an exterior wall w/o exiting my house.
You have no evidence that it worked perfectly. What you have is evidence is that it will fail perfectly, i.e. a miss will not overpenetrate walls.
Tell all that to the guy tried to get into my Grandmas house, oh you cant he died, he was shot with bird shot across a kitchen room was like 12 feet or so.
Any load can kill at any time. Out of any gun. If someone is after you in your house do not feel undergunned, just shoot the bad guy.