True, but when spring loaded bypass valved PD oil pumps are in relief, they typically still put out some increased flow with increased RPM, so they are not really perfect constant pressure devices unless it's some accurately computer controlled oil pump with closed-loop pressure feedback.
And even if they are in relief, the volume of oil supplied to the oiling system should still be adequate and above the required minimum level for proper lubrication if the system was designed correctly. When the supply volume is adequate, then the oil formulation and viscosity (HTHS and resulting MOFT) between the moving parts is what really matters.