Chain movement carries the oil to the bottom of the bar first. Most of the oil will be flung off at the nose and there will be less oil on the top of the bar where the cutting action is taking place.
.
I agree oil will be flung off at the nose, but I think 820ward is right about top of bar getting oiled first. Down side about cutting with top of bar is more work for the nose/tip of the bar. Been lurking here for a while and in hopes of small contribution although maybe should have kept my nose out of this???