You are exactly correct.
There may be good reasons to replace a shotgun with an AR-15 type rifle. The rifle is more precise, has longer range, and less likely to hit an unintended target.
But the idea that criminals are using AK 47 rifles in any significant amount is rubbish.
Writing to you live from Miami-Dade, I can tell you they're not. Most violent crime is the street and drive-by stuff in the hood, all too often with bystanders (little kids even) getting shot -- not with AKs, but with the usual handguns. This is a precautionary measure against a terrorist or gone-postal scenario. We know that happens.
Preposterous! Didn't you see "Scarface", or "Miami Vice"? /sarc