Ordinarily there are differing affects made from varying causes. The oil film here keeps the cam from touching the alloy bearing when fully pressured with good condition oil. If the film cannot Support the load that the rockers put on the cam then as it breaks that film, it usually starts to wear the bottom cam bearings first.
You'd get a different effect if you have hard abrasive particals reaching the bearing site, it usually embeds itself into the soft alloy and starts to cut into the camshaft. Obviously the two are very different.
If you've got that much wear on the cam bearings, then the big ends and mains I think could have also been at risk. While it's appart, I would be inclined to check them.�
It's why the oil condition is sooooooooo very important, above all else, when running these motors.
