Well lets take that to the extreme then.
Lets say you engineer an orifice size , that passes 1 qt of oil in 1minute at 30 psi. Now what happens when you try to jam 1.2 qts through that same hole in the same 1 minute?
Because liquids do not compress. The pressure behind the liquid will go up but the amount going through the orifice will be exactly the same. It is why our brake systems work. There is basically no flow in a brake system. Only pressure.
I also do not believe that high volume pumps cost horsepower when operating at the same pressure level. When you prime your engine with a hand drill there is no resistance or horse power usage until the galleys are all full and the resistance to flow begins. Then the drill begins to load. But up until the galleys became full, that pump was moving the oil into the galley with virtually no resistance. I believe that a certain pressure requires a certain horsepower usage. It makes no difference whether it is stock volume at 70 psi or high volume at 70 psi.
I also agree with that the pumps do not dump oil back into the pan. I see no opening on the small block pump where oil can exit out of the pump body. It is recirculated within the pump until the excess volume is required again. My opinion.