Wasn’t it (the necessity for a banana groove in the shaft) a hydraulic vs solid cam thing? With a hydraulic the rocker is never unloaded and therefore doesn’t get oil without a banana groove whereas a solid oils during lash
I don't see this as a logical reason needing a groove for hydraulic vs solid.
There are some generic shafts out there that have the oil holes located wrong and not centered in the rocker, pretty much outside the bushing area.