Hi Hubert,
I agree that the likelihood of these particles getting to the mains or big end bearings is pretty unlikely. At the same time, I'm a bit of a Nervous Nelly about particles getting splashed around onto surfaces where they shouldn't be (cam lobes, cylinder walls, etc). Plus, I don't like them up on top of my cylinder head where the oil return lines from the breather deposit the flecks with enough "force" that some of them stick to the valve cover. Surely some of those flecks get where they shouldn't be.
The bottom line, IMHO, is that those particles belong no place inside an engine.
Regards,
Gregory Bender