Some people distinguish between "major thrust" and "minor thrust". Minor thrust is the wall that the piston is pushing on during the compression stroke, and major thrust is the wall that the piston is pushing on during the firing stroke.
Looking at the front of a normally running (clockwise rotation from the front) engine, the right side is the minor thrust side for all cylinders on both sides of the V,and the left side is the major thrust side. Put another way, the driver's side of every cylinder is the minor thrust side, and the passenger side is the major thrust side.
So, from the driver's seat, the right side of all cylinders is the major thrust side. So it makes sense that the oilers in your brother's engine are pointed that way.
