Oil pooling in the lower cylinders shouldn't be happening unless the valve guides are worn, but it does happen. The engine design makes a big difference. Some engines were natural leakers. The older radial engines with rocker bolts that ran through the rocker head were often sealed with an o-ring under a conical washer. It didn't take long before the o-ring hardened or was heat-damaged, and took a set. We were always replacing those.
In the Wright engines, pushrod tube seals were hose clamps over hose sections, over thin metal tubes and the nipples on the cylinder and cam follower housing. These tended to leak after just a little time, requiring frequent tightening (which also caused leaks) or rotation of the clamps. The good news is that cylinders got changed often enough that the clamp problem took care of itself, most of the time.
Larger radials used separate oil tanks. I don't know what the rotec uses. It probably still faces an increased potential for oil in the lower cylinders, as well as oil resting on the backside of the pistons on the lower clyinders, causing more oil to present on the cylinder walls.