* True, in the strictest sense an oil pump just moves the oil (like that Zen conundrum of the single clapping hand). It doesn't, by itself, create the pressure. The clearances along the oil pathways create the resistance-to-flow and pressure is a measure of that resistance. Increase the volume of oil delivered while keeping the oil clearances the same increases the pressure (e.g. increased rpms). Increase the clearances while keeping the oil delivery volume the same and the pressure decreases (e.g. worn bearing inserts).
* So, what it means in useful terms is that you need to determine whether the oil pump still has the capacity to deliver the oil. You do that by looking at the condition of the pump rotors and housing, and measure the rotor-to-housing/rotor-to-rotor clearances (clearances are by far the most important thing; a few scratches won't matter much).
* If you've also found your excess clearance problem (beyond the oil pump) along the oil pathway (like a scored bearing or journal), then you've got both delivery and resistance and your oil pressure should be back to normal.