I was always told to only move the Hydraulic selector lever when the lift arms were in the lowered position.
You are changing the linkage inside to switch modes and that is best done lowered.
My understanding is that the draft control mode senses pushing AND pulling on the top link. (a plow pushes)
The system tries to maintain a constant force on that link. For light work, you have to have the control high up on the quadrant.
Also there are 2 places to attach the top link to the tractor. The lower hole is for heavy draft work. The upper is for lighter work / more response.