Pump variables are confusing. Take just the pump alone. The spring pressure on the relief valve is just a part of how it works. Most are a ball bearing(some are a piston). Some sit on a seat and some move past a port. Sticky ball or piston will raise the pressure, no matter what spring is holding it in place. Add a filter system with a relief valve and it can get more complex. The pump has clearance considerations as well. Most pumps are "gear" type. So the gear mesh matters(like a pinion and ring) but most don't think about the end clearance between the gear, body and the cover. There are "restrictions" in the system as well. You may have a case where all of it adds up. Close the restriction to the valve oiler line. With the same volume of flow, it will have to go somewhere. And yes, volume matters. Close main bearings, and close rod bearings, and a bit of restriction, may lift the relief valve. That does nothing to reduce the volume the pump is moving. And the volume alone may be enough to keep the pressure up. Most engineers would worry about too little flow to moving parts. Too much is an after thought. Oil pressure that stays "high" at full temp. Should indicate a restriction some where. The "pressure" will be different in different parts of the system(I know, counter intuitive) but it is still a system based on volume, flow and pressure. Not as simple as a garden hose. Over oiling can cause issues you don't want(leaks, lots of leaks).
