[Lynn Eades]

The long fitting restricts the direct internal flow to the main bearings and diverts a portion of it through the cooler, just by the fact of the fitting partially blocking the gallery.
Btw. The cooler bypass valve is to let the oil flow continue should the thick cold oil of the day refuse to flow through the long lines of the cooler system) I have installed a full flow filter in my oil cooler line so that as long as oil goes through the cooler it is getting filtered (under normal circumstances, with modern oil, it will never "not" flow.
The two fittings found in the back of a U.C. engine block are in the attached photo.