Food for thought, If you were designing a relief valve from a 'Clean Sheet of Paper', would you:
A. Put it in the
oil pump so that the relief is
oil squirted back into the incoming
oil and thereby create cavitation & air bubbles into the oil system along with having your oil pressure set/regulated a considerable distance away from the bearings.
B. Install it as close as possible to the bearings & relief flow is directed back into the pan or valley in such a manner that it doesnt create windage & any entrapped air can seperate.