The coast distance may have something to do with it, and the lowest speed. I haven't taken measurements that much but I never noticed a dramatic change in fuel economy. Granted, I tend to engine-on glide and the retarded ECU thinks you need 1000rpm to maintain the headlights which hurts it.
However, I never let the speed of the car drop below 50mph because I don't want to be the target of road rage. Doesn't help that my car is light, the speed drops very fast due to drag. On top of that, it feels like revving the engine up past 3000rpm to match revs each time I pulse uses a nontrivial amount of fuel as I do have to push hard on the pedal to get it to rev quickly (that shall change a bit when I put in a 9lb aftermarket flywheel
). To travel one mile at an average speed of 55mph, doing 50-60something pulses, I have to use like 5 pulses, that's just too much for me. I'm trying to cut the aero drag down a little so I can glide down steeper inclines such as the Bay Bridge at a full 50mph, but for now I tend to pulse up hills and glide down hills, and just cruise at a constant speed on flat land.