I think the rationale was that the large oil filter with the “heavier” valve would act in such a way where it would raise the oil pressure in the system because of the increased resistance to flow. It seems like a questionable way to get some additional PSI at the risk of reduced filtering.

 

I think the large oil filter was that monster of a filter off a diesel truck. The PH8A size was used for many many many years on RRC's. Then LR started to use the smaller PH16. The specs for the those two were dead even if I remember correctly minus more filter media.