I think the pictures are misleading you though. The bearing you see that is worn to the copper is actually more severely worn through the center section and less on the edges. It is silver through the center because the copper has completely seperated from the steel backing. The only copper remaining is what you see on the edges. It appears that the chamfer done to the oil galley has "dug" into the center of the bearing while it rotates and carved it out. This could have been due to an accidental lack of micropolishing on that journal after the crank journal galley was chamfered.