From what I have seen after investigating complaints of this sort is that nearly all cases are the result of people that had defective meters that ran slow now get accurate measurements. In other words they were previously being undercharged.
This kind of thing would happen whenever meters are replaced. The case here is that meters are being replaced wholesale, therefore giving hysterics the opportunity to get hysterical all together.
I wouldn’t necessarily bet on an old watt-hour meter being THAT slow. And who’s to say some of the smart meters aren’t fast?