It does show up in fleet vehicles, a lot. Mostly, as stated with oilfield vehicles. There are vast amounts of Ram 1500/2500 trucks that all have camshaft/lifter issues up here. The instances of 300s, Chargers, and Challengers having these issues is lower, at least up here.
I think the problem on the Hemis is that the areas where the splashed oil can get to the cam/lifter interface area are too small, so not permitting enough oil to get to that area. The thinner oils may be a contribution factor. However, the non-roller cam engines were engineered to use oil that had higher levels of zinc (mostly, but other metals as well) than current oils do. The Hemis, being a much more modern design, and using roller lifters, should be fine with the lower zinc levels.
I think that there may also be an issue with the amount of surface hardening of the cams. Maybe it isn't as hard as it should be, or that the hardening is not going as deep into the lobes as it should to allow for a long life. From your own pictures, the rollers on the lifters look fine, but the cam doesn't. As well, not all of the cam lobes are chewed up, which may mean that only one lobe is improperly hardened, or is starved for oil. Just guesses
