Volume of oil being pumped is more important than pressure.
I disagree with that. The physics of that statement is just wrong. Here is why. If I have a pump that is feeding two locations, and the pump pressure is 30 psi, then chances are that unless one of the two feed lines is blocked, I can assume oil is getting to both locations. If one of the feed lines is blocked, I may be in trouble even with 30 psi.
Now lets open the feed line (to simulate faster flow to one line due to a drop in viscosity, less back pressure due to less resistance to flow), to one of the 2 points of use, so much so that the pump line pressure is now essentially zero at the pump outlet. If there is any restriction difference between the two, back pressure on the second line, or if the flow is larger to the first line, it is possible to have negative pressure, (sucking) on the second line, it is called back flow!!!! When the engine rpm slows, and the pressure is dropping, it can also cause back flow from line 1 to line 2 as the pressure drops.
At best, at zero psi, you can expect the oil to take the path of least resistance, and not flow to places where it takes more pressure to get the oil to the spots where it is needed most. Imagine a pipe tree, with an outlet at an elevation of 1 foot, and another outlet at an elevation of 10 foot, then imagine you have the pump running at 15 foot of head at the pump outlet, gauge pressure. Now you throttle the pump to where the pump outlet gauge reads only 2 foot of gauge head pressure. At that point the flow of water out of the top outlet 10 foot of elevation will be ZERO!!!
Also you are assuming that the oil pump is pumping (actually moving) the same volume of oil at 200 F that it is pumping at say 100 F. But if the pump gear teeth are worn, it may actually be pumping less oil at 200 F than at 100 F, with the pump at equal speeds (same idle speed) as it is easier for the oil to slip and leak backwards through the gear teeth when its viscosity drops too much!!! Many of today's MV oils use polymers to simulate the high mol weight at operating temps, but these polymers have a bad habit of shearing and letting the oil viscosity drop on long drives at high temps and higher rpms. Some formulas seem to hold better than others!!!! When the oils cool off (like for an hour or more) they seem to recover from the high shear.
I notice the high shear effect when driving at 60 mphs for 30 minutes or more, but do not notice in stop and go driving for an hour!!!!!!