How did this happen to my pushrods?

I've been chasing a high RPM misfire for a while now and I'm pretty sure that it's being caused by tired old valve springs. Anyhow, I pulled apart the rocker assemblies and pushrods for inspection. The rockers and shafts look great but the pushrods were coated in sludge, I'm assuming from sitting for a while before the previous owner did a basic rebuild on the engine. I noticed a kind of spiral pattern on about half of the pushrods but I thought it was just how the sludge built up over time given that the pushrods are always spinning and moving up and down. I decided to clean the sludge off and found that the pushrods are actually scored in this spiral pattern.

I'm wondering what could have caused this and is it anything I need to be concerned about? When the rockers and pushrods are assembled and in place the pushrods don't appear to be rubbing on anything, not even close really. Even if they were rubbing somewhere, how would they end up with a uniform pattern going all the way up and down the length of the pushrod?? Anyone seen this before?

Also, the ball ends look great, they have a mirror finish and no burrs or scoring of any kind. The pushrod looks a little bent in the picture, it's just the shadows. All 16 are actually dead straight and roll across my stainless steel workbench perfectly.

Thanks everyone