Bearings are protected from physical damage only by oil pressure. Pressure is cause by resistance to flow - in bearings' case that comes from proper clearances and properly shaped (parallel) surfaces on the bearings and crank's journals. Especially on the mains, where the oil is pumped in, and then has to go through the crank to the rod bearings, journal finish and clearance is critical. I like a main clearance a little tighter, beacuse there's less leakage before the rod bearings get it. If the jourrnal(s) are tapered, the oil can escape and will not have a consistent load carrying capacity. This can be very localized on the bearing. Too loose is worse IMO in a main clearance than too tight. That's what I see on yours. The journal surface isn't truly flat, and the oil clearance may be a little too wide at some points around it. Remember the bearing bore is not perfectly round - it's tghtest at the top and botton perpendicular to the cap parting line. If the crank is not flat and the journal a little small because it was only polished you're asking for problems in the long term. Contaminants will scrape along the bearing making scoring down into the copper, or embed in the surface where you can see them. The marks are a bit different than yours. Oil starvation even at startup would affect all of them, and #s 1 and 5 are fine. So it's something else in my opinion. If you didn't measure (you used plastigage) you simply don't know if the journal was good. You know the clearance was in spec. If as you say the shop said it was marginal but usable - I'd say that's some confirmation. The Arnold gage they use is much more precise than a micrometer. A mic will see the taper if the temperature is right, enough measurements are taken, and the person measuring can read it correctly.
