Chris, 

I think Thomas is referring to the spring/check balls in the crank that block the oil spray into the rotors at low rpm.  The purpose of the oil spray is to cool the rotors.  To my knowledge, there is nothing that inhibits oil to the bearings, unless you consider the pressure relief valve as doing that, but it only controls high pressure.  

Mark 

Over the years Mazda used different schemes to warm oil rapidly. One was a thermal pellet in the font cover that could bypass oil around the oil cooler lines. Later the cooler had a bypass thermostat that allowed oil to bypass the cooler. Later still the crank had a thermal pellet that limited oil flowing to the rotors (Spray nozzles) to speed warm up. In most 13Bs there is a pressure relief in the front cover that opens at 144 pounds to prevent that pesky "O" ring from blowing out on a cold start. This valve dumps over pressured oil into the sump. Had it stuck open, there would be no oil pressure. Can be seen with the pan off.

 

Lynn E. Hanover