High crankcase pressure would raise the hydrostatic pressure of the oil on the sump pickup, while acting as a restriction for the oil spilled from the bearings, cam, lifter, piston squirter and turbo return back to the pan.

Of course, for the effect to be large enough that it's measurable, he'll probably be blowing white smoke from the exhaust, unless he was using an unusually effective air-oil separator.

 

I don't think crankcase pressurization could be the cause. Only 3 psi of crankcase pressurization will cause substantial smoking. And producing more than 3 psi would require a really bad ring seal combined with a non-modified (stock) crankcase ventilation setup.