I use mine to control lift speed with the position control lever. When using my 3pt rototiller. Set it to lower flow , when I raise my tiller out of ground it comes out nice and slow and doesn't leave a divot. It's main function is to control rate of correction for draft control as you said.It's for draft control reaction speed, not "lift speed" per say. It only comes into play when you're using ground engaging implements like plows and such with draft control. And you have to have your reaction pin in the correct position. That's why the knob frequently "freezes"--Not many folks know how to use it.
The knob on mine was missing so I made a lever. I only get about 30 degrees of movement. I typically leave it on fast but move it once in a while to keep it free.