Oh, it will. Goes out the crankcase vent, just like blowby. Usually max combustion pressure is around 800 psi, full throttle, but drops to 60-80 around idle, but it has to push oil in the slip/gap outta the way first, takes time. Leakdown tests can reveal headgasket leaks, helpful if you can probe around it with a hose jammed in your ear. Worst case, of course, is the complete burnout/blowout of the headgasket crush ring. In this particular scenario, however, the oil infiltration has been hampering ignition, so his engine hasn't been able to stress the suspected leak zone...
Also, as the piston travels down, the cylinder pressure drops, but there is also a complementary momentary increase in crankcase pressure from the displacement of the backside of both pistons, before it gets vented. Aids in shoving oil in there...