I been studying hard the oiling in my stroker I am building and it seems the full groove would help the rod bearings live longer because they have access to pressurized oil when the cylinder pressure is highest. The 1/2 groove only sends pressurized oil to the rod on the bottom half of the stroke. Weather or not that amounts to a hill of beans under dynamic conditions I could not tell you but it does seem odd they do it that way from the factory.

In order to keep more oil on the crank on mine I drilled smaller oil feed holes in the cam bearings as they are getting fed right off the oil going to the mains. When everything is done right in a SB oiling don't seem to be a big issue from what I have seen. I almost always use standard volume pumps and don't seem to have much issue getting enough pressure.