That's not "Adaptive" in the sense that they're talking about here in my opinion. That's just an offshoot of what some companies will call radar cruise, to where the car maintains a set position behind the car in front of you. I like the premise though, I'm sure it works rather well - and on long highway drives, I wish I had it.
In my personal opinion, I would think an adaptive cruise would work similar to what I do to attempt to get a leg up on milage. I have a car with a pretty healthy v6 in it - and it also has an instantaneous MPG gauge. The hills around here aren't many, but if I control my speed +/- 10 mph to the limit (up to -10 on a long uphill, +10 on a downhill) I can keep my milage in a much better range than the cruise control attempting to limit me to +/-2 mph when set. Over the course of a tank, I've seen a 2-3mpg gain, which translates into real (albeit a small amount of) money back into my pocket.