These grooves have been there since the beginning of the automotive age, it seems, and they have always been there to oil the cylinder walls. It is wishful thinking to think that they are for oiling the camshaft. They don't aim at it, either. Most camshaft oiling has been by splash, with oil getting past the lifters and some from the valley supplementing.

When you're building an emissions controlled engine you want to keep as much oil out of the combustion chamber as you can. It seems that there is enough oil mist in the crankcase to oil the cylinder walls without those extra squirts from the rods. The use of lower-tension rings to reduce friction also makes extra oil on the cylinder walls bothersome.
This explains the general trend away from these grooves.
For the high performance engine, extra oil in the combustion chamber can cause knock, as oil has a much lower octane rating than gasoline.

R.