I think Jerry indicates pretty much what I think. They used to use a term "washing the bearings", which was applied to engines with so much pressure that the
oil didn't stay long enough within the bearing area to create a film to carry the load. I don't know what clearances were being used, but bearings all bleed off and in order to increase pressure you have to pump the
oil through the passages faster. It would seem that this actually prevents a film barier from being created.the They usually suffered from fried bearings.I also agree that it is volume more than pressure that is needed.