Yup thats exactly right. I installed the Delta-FL (it might have been a knockoff, cant remember the brand) but its the same stuff. My floor is only 7 years old, but I'm positive there is no way it was within 1/8" every 10 feet. It was not shimmed at all. They also recommended letting the ply "float" on the stuff. My contractor and I thought that was nuts and anchored the ply, through the delta, into the concrete. Sure it penetrates the vapor seal a bit, but the floor is rock solid sturdy, and there are no squeaks and its still got "bounce". I'm not worried about the seal being broken by the few anchors as the heads are driven so deep into the wood its sealed.
All in all, Im REALLY happy with it. Even without the carpet on there is a HUGE difference. Its nice to walk on, and it really reduced the moisture (humidity) in the basement.