I saw an experiment in a magazine back in the late 80s early 90s and they put a perspex window in a sump so you could seee what was going on and the crank acted like an egg whisk, with alot of oil trapped in the rotating assembly like when you whisk an egg.
Knife edging will make it more aerodynamic so in theory is should cut through the air/oil/blowby gasses or whatever else is there more effectively.