I've read a number of LEO AARs RE: Birdshot. Ugly, nasty surface wounds, w/o much penetration. Body armor, drugs, or drunk is always a possibility in somone who has the mindset that it's acceptable to invade somones home.
I'm still not down with Hevshot until I run my own tests and comparisons, but, your point is well taken.
You might try sending a few rounds to Old_Painless at
http://www.theboxotruth.com and have him run some penetration tests. Might be an eye opener for some people. He's a really good guy, and some of his tests are pretty illuminating.