This is true. The billsteins I guess would be classified a load leveling shock. They have an adjustment on them to adjust the compression so in essence adding or removing lift I guess.
The 5100's? Interesting, I didn't know that. From my understanding you can adjust the dampening, and make it stiffer, but I didn't think it would raise the vehicle at all, unless they are a coil over type shock.
The springs are what the vehicle rides on, the shocks (should just be called dampeners) control the rebound and compression.
I know for a fact that actual load levelers, like this one for instance, will raise the vehicle an inch or two in the rear. Had a set of gabriel load levelers on mine for about 2 years, they worked very well and didn't squat at all when loaded.