That 1988 SAE paper has been cited a million times.
Its part of the reason why you see Fram Ultra recommended so much on here. The Ultra's depth filtering capability is unmatched.
Ultra: 99.5% 20 microns, 94% 10 microns, 80% 5 microns.
BTW, when you read about "clearances", its all true that some particles slip past parts inside, yet understand that boundary lubrication happens inside an engine on loaded surfaces and the distance between rubbing parts can go to very near zero, so that a 0.5 micron soot or sand particle can cause extra wear too.
Bottom line: the cleaner the oil, the better.