Yes, those are Roadmaster Active Suspension.
They do lift the rear up to an inch. But you can reduce the spacing between the coils and reduce lift to 1/2" or less if you want.
They really help with bounce and jitter on rough roads, and axle wrap. Make the unloaded ride a tiny bit stiffer but not bad IMHO.
Help a bit when you're loaded up as well, especially with my F150, but I wouldn't think you would need them when loaded in a 3/4 ton. Your overload springs would do the lifting then.
Surprised to see them on a 2500HD.