Crow, I wouldn't agree the test has no scientific foundation, but suggest a couple of things for consideration.
While choke is a variable with shotguns it would serve well to actually pattern a gun with the load of choice and remove the question marks. Choke is not the only thing that affects pattern spread. Velocity is a big player as is shot column length. I've done a fair bit of shotgun reloading for clays and game shooting. While deep into the world of shooting clays I started loading 20 ga equivalent loads for the 12, ie. 7/8th oz of shot in a IC choke. It shot very much like a FC barrel from a pattern perspective. That said, I have an old 12 bore with a 28" FC barrel that will confine a load of buck in a 10" pattern at 25 yards every time. One simply does not know what will happen with scatterguns until you head to the range and find out what the facts are. Likewise, many subscribe to the idea that more open bores shoot Forster slugs better than a FC. Yeah, maybe, sometimes....but the referenced 12 bore barrel above will shoot stunningly well with such loads. As in dead hog out to 75-80 yards every time. And a load of #8 shot will make a quail bird pretty much vanish out near 20 yards.
Your test geometry is biased by the premise that a load dispatched at the perp will strike the wall at a 90* angle give or take. That is statistically unlikely. Given your test at 6 yards, 90* impact, try it again with maybe a 45* angle and see what happens. To illustrate the point, imagine you confront a punk in the hallway. Any shot that goes wide will have a much shallower impact angle and this will cause far different results. Too, keep in mind that while some shot may in fact pass thru 4 layers of drywall, given the variables in home floor plans, it may be more, or less. Regardless, innocent souls on the far side will suffer less from shot that has made that journey, both in number of strikes and depth of penetration.
With all that out of the way, consider this. Every home has variable geometry and in some portions a 6 yards shot might be long. In others 15 to perhaps 20 yards is a possibility. So it is in my present house and one I lived in some years back in Georgia offered a shot that might have been closer to 25 yards. The variability is large and circumstances are one the home owner has more control of than the punk. Keep that in mind when you become alerted to the fact that someone is trying to break in or has already gained access to your home. It is a point where the home owner holds the advantage, a position not to be surrendered by yelling "Who's there?!" Nope. Keep your lips zipped, grab your cannon and quietly keep your grip on the high ground. One can seek out the punk, or let them come to you, your choice. Make the call, show no mercy. Better the coppers listen to your testimony in lieu of both sides of the debate.
