It kind of looks like the edge of a main bearing, but the radius does not look like the right diameter. I would expect an
oil pressure drop if it was from a rod bearing. I'm not sure a main bearing would cause an
oil pressure drop, if the thrust end wore off. I don't know if you could measure the crankshaft axial play, while the engine is in a car. The transmission may limit movement and give a better reading than what it actually is.
Hopefully it is something else. You want someone, who knows more than me, advising you, either way.