Magnum camshaft bearing mystery

I have 2 360 magnum motors that I purchased used. Both have over 100k on them. Both were exceptionally clean inside. No sludge, cylinder wear at a minimum, etc. When I went to change the camshaft, Both had weird wear and damage on the #4 cam bearing " see pics"20220516_163852.jpg 20220516_163835.jpg No damage found on either camshaft. Just curious if anyone else has noticed something similar and maybe an explanation.