im not sure how many of you have ever actually BEEN in an engine assembly plant, ( I have been in quite a few) or fully rebuilt, block up, any engines, but -most- of what you see on the plugs in these threads is swarf from assembly, NOT items wearing in. there is a *tiny* amount of color from the rings seating and the clutch plates wearing in. If I rebuild a motor, from scratch, by hand, with all new parts and anything like I've seen on the magnetic drain plug came out like i've seen on here in the 'plug' threads, I'd tear the motor down. they zip in fasteners with power tools really quickly, all new threads and there is some discharge from this, and it gets into the cases. also flashing from new parts, etc... get on youtube and look at vids of people breaking in motors, then cutting the oil filter apart to look at the pleats to check the contamination. while leaving the break in oil is fine, as these particles really aren't going to get back into the oiling system and circulate.... changing the break in oil early also does no harm and removes the big chunkies from factory assembly.
i swear i had -zero- swarf on this, but i also chased every thread and unloaded a few cans of brake clean on it before i started assembly., after i deburred the block, etc. the -only- coloring i saw was a slight silky grey from the rings seating & the moly lube from the cam lobes. the factory DOES NOT take this much care mass producing a low cost motor like we see in the grom, trail monkey, etc. of that i can assure you. and, it doesnt matter.
want to see a real horror show that doesn't mean squat? go to the briggs v-twin engine plant in Alabama where they assemble with self tapping screws in the motor.
Been there, saw it 1st hand on the line when I worked at Desoutter.