You are correct ,
I cannot see all of them.
But remember what is on my Engine now is a old original set of 273 rockers with Factory banana grooved shafts.
I just happened to have from a boat engine someone gave me.
They showed little to no wear, I cleaned them up used them for several thousand miles when the first set of PRW Rockers wore out.
When the second set of PRW Rockers wore out recently, I dug back out the 273's checked them over they still show Zero wear.
They are back on currently and seem to be just fine.
But I do plan to pull them off and re inspect.
When I do I will post pictures and how they are holding up.
I think your right about the oiling grooves that is pretty much proven here.
PRW Rockers failed twice with no grooves.
Old original 273 rockers have not with grooves.
And they are 55 years old...
Mike