I'd be surprised if that's what happened. I suspect this is just another unrealistic number that's the same proportion of reality as the previous numbers.
That said, when I'm traveling and going for extended battery life (read: trans-atlantic flights) I get pretty close to the rated number by dimming my backlight and shutting off wifi and bluetooth.
Apple reported that they were changing the way they measured/reported battery life with the last MacBook air launch, and explained that it was less favorable, but more realistic.
During transitions like this it would be nice to give both numbers on the new and old machines. This at least gives people some type of comparison point.
