Yeah but getting your rotor and concave setting matched up to the crop an the state its in makes all the diffrence as to the capacity of your sieves.
Goes without saying in stuff like sunflowers where the trash often has the same weight as the seed!
Besides, people tend to panic on the samples, they do not have to spotless anymore, its not like we are harvesting 5-10 ton hour anymore. We are up around 45-50 ton hour these days and it goes without saying that it takes alot more to sort that volume out.
And finally, in the end of the day: combines are grain harvesters, not seed cleaners.