While this isn't what they necessarily said, to add another point of view, consider a population X which has a job option A, and a equally-sized population Y wh

While this isn't what they necessarily said, to add another point of view, consider a population X which has a job option A, and a equally-sized population Y which has options A and B. In this simplified-beyond-reality model, it would be fully expected that Y will not be "equally represented" in job A. It also won't be "equally represented" in job B, as it will have 100% of the positions. This is not a complete explanation of anything, but a tidbit to keep in mind.