[Def]

Factory engines need tight mains to account for wear/scuffing of 200k+ miles of cold/semi-dry starts.

On a lower total mileage, but higher HP engine you want to open up the clearances slightly to make sure you get enough flow to always form the hydrodynamic bearing at higher RPM.

Tight bearings are much more likely to squeeze the oil film down in "heavy applications" just enough to "starve" the bearing of additional oil flow long enough to scuff it up badly (only takes a few microseconds).

This is not a case where more is better, but generally on the high side of OEM clearance, or even higher on some special cases is what's called for on a higher HP/lower total mileage build.