Opinions are opinions
Facts are facts
Yes bird shot kills at close range
No it will not penetrate multiple walls
All the links you have posted against birdshot as HD are either people voicing options with no facts to back them up OR the videos that have "proof" are at greater distances than one would see in a typical home.
If over penetration is not important to you now, when SHTF and Big Bubba is you new roommate... Over "penetration" won't be important to him either.