There is also another anomoly and that is the filter is really in second priority to the "FLOW" capability, capacity of the system. This is the primary reason for the "by pass valving" built into the filter. Along with that, the filtering can not be so "FINE" as to either impede or restrict the flow in anyway. Of course there are working specifications for this, but at our level, suffice to say, even if it were common knowledge, it would pass right over or under most of our heads, even on this august board.
The proof in the pudding in this, is even on this "enthusiasts'" board, how many folks actually have bypass oil filtering and pre oil systems!!?? By almost any measure this meets the definition of "fine" filtering.