The idea behind the pre-luber was to have oil pressure before you crank your engine, and after the engine is shut off.
Mine has a brain-box which is really a timer that controls when the pump comes on. So you get in the car and turn the key to run (just before start) and the pre-luber pump comes on and pressurizes the oil system to prevent dry starts and engine wear. Once you hear the pump shut off you start the engine. So your oil pressure warning light is off (or your oil pressure gauge shows positive pressure) before you ever crank the engine.
The bigger benefit was at engine shutdown; the pump would come on and run for a period of time to cool and lubricate the turbo bearings while it was spinning down; which greatly extends the life of the bearings. The turbo on some engines will spin down from some hundred-thousand RPMs for some minutes, and without oil to cool and lube them they get hot and what oil is there cokes and sticks to the bearing surface.
A side benefit was after an oil change. You would run the pump for a couple cycles to fill the filter. Some lube places didn't like to work on turbo cars because after the oil change they would destroy the turbo waiting for the system to fill and pressurize. If you think about when you change the oil in the 6.2, even though I fill the filter before install, the oil pressure warning light stays on for 20 seconds or so; now imagine an engine where you can't fill the filter body with oil, that light will stay on for 30 seconds or more, and if you had a turbo spinning there with no oil going to it for cooling and lube it would be destroyed.
One other side benefit was you could install a QD fitting and use the pump to drain the oil; useful for a few weird cars that had difficult-to-reach oil pans. Boaters use them for this reason.
A different branch of the prelube idea was one that used an accumulator. The engine's oil system would fill and pressurize a small accumulator and at shut down it would meter oil to the turbo bearings. It has limited applications but is much less complex.
On my little 4 cylinder Mustang II it would run the pressure to 50 psi before start. I never got the turbo installed so when I sold the car I took it off. It's in line to be the pump for my used-motor-oil-trans-fluid system for moving the oil slurry through a filter and into the tank on the M1009.