"Position" control and "draft" control are two different animals.
For a better understanding of "draft control" do a Google or other search for "Ferguson System". Ferguson brought out the first real draft control, licensed it to Ford, and then had a falling out. It's an interesting story of industrial espionage, corporate shenanigans, and contractual disputes ending in the courts.
(Just as an aside: an old Ferguson or Ford has a better draft control than virtually any modern machine.)
(Another aside: JD reacted to Ferguson by bringing out a competitive system that is considered by experts like Nebraska Tractor to be inferior in every way.)
Position control nothing more than using your 3-point to lift an implement--like a brushhog or mower or rock box or platform or whatever is hung on the 3-point.
As long as the motor is running, the setting should hold the implement. Engine goes off, implement sometimes-often-usually drifts down over time. Usually drops faster the older the machine is as seals wear.
Draft control is for soil-engaging implements like plows or disks or harrows or subsoilers. These implements are all designed--when properly secured to the 3-point lift and adjusted correctly--to "dig" into the soil. As you pull forward, the implement wants to "dig" deeper.
The true draft control exerts hydraulic pressure to lift the implement 'up' to counteract the "suck" (a technical term in the industry) of the soil.
You continue to drive forward, the implement sucks down, the 3-point lifts up---its a continuous balancing act. Have someone else drive a machine with draft control while plowing and you can watch the implement move up and down as the hydraulic system pulls up against the soil suck.
All that said, I'll bet your machine doesn't have a true draft control.
Please post back your continuing experiences so we may all learn.