From an engineering perspective...
Going to a thicker oil and seeing more oil pressure can be an illusion of improvement. Pressure is caused by resistance to flow, but before I go too much further, I'd like to point out that since the oil pump is a positive displacement pump, that the relationship between the flow of oil A to oil B, is somewhat equalized by that fact. Back to pressure and flow, as the pressure is higher, the thicker oil could be actually flowing less due to more resistance of trying to get through the journals. An adequate flow of oil is important, whatever that volume may be.