Oem tires and wheels, both of which are built to tighter tolerances, and tested and marked for runout and road force variance, and match mounted stiff spot on tire to low spot on wheel.....still take some weight to balance... and sometimes a fair bit...
Getting a zero weight balanced wheel/tire assembly is just luck... In my driving experience, with probably 50 tires or more, in many brands, I think I've had maybe 2 or 3 that took no weight, one recently being a Toyo winter tire.
And I took that one back because I wondered if they forgot to balance that one...!
I think oem wheels put on a thin clip or similar to show that the wheel has in fact been balanced.