That Cyclon is what, 10 years old? Fora was doing this at that time as well. I think the notches do little more than allow the gas to flow out of the crank passage, which in these engine is a very large portion of total crankcase volume. I have a Stels where the crank passage is not drilled concentric to the journal. I think was done to assist balance though. Some of the older Rossi engines used sealed bearings and relieved crankwebs wrapped with a band to reduce crankcase volume.

It's all a big game of design compromise. You want the engine to breath well so you increase the crank passage diameter which increases crankcase volume. You shorten the rod to increase primary compression. Now you have piston skirt interference. So you cut off the skirt where it isn't needed and notch the backplate for the skirt that is. The rod can't be so short as to let the piston cover the transfer passages. And so on.