Unfortunately there is as much ignorance about terminal ballistics among police administrators as there is on internet gun forums. They made a poor choice.
Although not provided in this thread, they substantiate their choice with logic and facts. The cartridge and rifle does what they set out for it to do. That is success, not failure.
A 5.56 is simply not a good choice for engaging a suspect in a vehicle.
Exactly - a poor choice. And who made the choice, at the time, to use that firearm with that cartridge on that target? That's right, the shooter. If they were ignorant as to the proper employment of the tool they were using, the only people who could be at fault are the guy who didn't know, and possibly someone who was supposed to tell them.
You use a wrench as a hammer and it'll sort-of work, but not as well as a hammer.
Define specially designed penetrating ammunition.
Ok let's rephrase that to specially chosen, for penetrating capabilities.
Over penetration is one of the reasons that 5.56 carbines are replacing 12 gauge shotguns and pistol caliber carbines and submachine guns for police use. Even 5.56 ball will not over penetrate as much as most commonly used law enforcement handgun rounds. While 5.56 penetrates, it's most likely to break up and lose energy rapidly making it less likely to injure an innocent then the handgun and shotgun rounds.
Now there's some of that mis-information you mentioned on gun forums.
Pistol and shotgun projectiles may penetrate more, in some substances, and at closer ranges, in some circumstances. But they slow down rapidly, and start off slower. This means they become less harmful much sooner, and gravity will pull them into the ground in a shorter distance too. I'm pretty sure you already know this, which makes it an academic debate.
As well, 5.56 ball's penetration capabilities increase the farther it goes. IIRC it's maximum penetration occurs at 600m, where it will pass through an entire bookshelf and the books on it. And, of course, the high velocity and b/c means that a flier can go several km.
I too like talking and reading about latest and greatest, and tacticool this and that, but in this case the only technology that would help would be a rifle bullet that would penetrate, but also slow down quickly.
And then people would be complaining about lack of wounding, and inability to engage targets farther away.