Yes I do have that kind of precognitive skill, its called common sense. The biggest room in my home is 15' X 25' wall to wall, so that is the range I'd be shooting at in my home. I don't know the distance this man got shot in the face with bird shot but I can promise it wasn't at 10-20 ft. Like someone else mentioned in that range it would be similar to getting hit with a slug. I've shot snapping turtles at that range with bird shot and i just punches a hole strait threw them. Is my home defense shotgun loaded with buckshot? Yes. Would birdshot effectively kill a man in a home? Yes, its not even worth arguing. I'm not saying birdshot penetrates more than buck. I'm saying it will kill an intruder at that range.
It is not like "getting hit with a slug", as it is a bunch of individual pellets whose mass is not combined. They slow down, and do not each have the same velocity as large projectiles.
You can kill a man with a 22LR, but the only advantage to using a 22LR over a larger centerfire caliber might be capacity, recoil, etc. Considering birdshot and buckshot using the same payload will recoil relatively identical, there is no reason to use the birdshot. Your shoulder won't notice the difference between the buckshot and birdshot, but the intruder's vitals will!
EACH individual pellet will slow down when it hits anything, which will help for walls, but the same principle applies to the badguy as well. It simply won't penetrate as deep. The problem doesn't lie with the "average" intruder. The average burglar will run at the sight of a 22, let alone a 12GA, but the problem arises when you have someone that is not "average", is equally armed, or drugged up. I don't know if you've ever heard of it, but Vietcong and Taliban alike have all used stimulants to boost their combat effectiveness. Without a CNS shot or a blow enough to take out vital organs they don't just "stop" as reality and pain tolerance is distorted. The average person does not break into a home, so I'd say the chances to find a meth-head in your living room if your house is getting broken into is probably higher than your neighbor kid down the street.
Why handicap yourself with a load that WILL perform substandardly compared to other loads. I wouldn't consider anything less than #4 birdshot, if you are "stuck" on the birdshot theory, but bigger is better for penetration. The FBI has penetration tests and minimums for a reason.