I saw a new tire balancing machine can show you where to align the tire and the rim to minimize weights

Which had me wonder...

Are rims balanced from the factories? Does Cragar, Weld, etc have rims tested for balance before they ship out? Or does the imperfections in tire manufacturing negate the perfection of a machined rim?

Would it make sense to balance a rim without a tire, and then use a file or grinder to take a small amount off where necessary to make a perfect balanced rim, and then, do the same with a tire?

Just wondering.