I load a female package car driver.
The number of pieces she gets is typically double or more of the other 2 cars I load. Today, I think she was forecast for ~650 pieces, including sure-post. Her car is almost always packed full. The other 2 drivers had, maybe, 625 combined.
The drivers definitely hold their own.
In other positions, yes, women are given preferential treatment. But, some do load - and quite well too. The others who don't make the cut either get transferred to an easy position or quit.