Originally Posted by Vegard
Polishing removes the 'natural' pits in the metal that would normally retain lube. So your theory is sound.
Pretty much what Vegard said and you're thinking.
If you check blue prints you often times see a finish call out, which is a number followed by a check mark. That's usually a max call out, often I see 32 or 64 finish call outs. So a max of 32 or 64 for the surface finish.
Thing is when you get down into the single digits and you get that mirror finish, nothing sticks to them. That's fine for some parts as they may need to shed oil, grease, or other things. But when you want it to hold grease, the grease can't stick to it.
So those mirror like finishes people having been going for on bolts are actually screwing them up. Not only are they changing tolerances (you can remove a couple thousandths and take the part out of round) but you remove the surface finish that's designed to hold the grease.
Even if you bought a BW polished bolt, that's polished to a proper size and finish by machining standards. When somebody does it themselves you don't know what you have. You may have a 2 Finish when you need at least a 16-20 Finish to hold the grease.