> Sorting and Wage Inequality: Stronger sorting contributes to wage inequality. High-skill workers employed by highly productive firms tend to earn substantially more, while low-skilled workers at less productive firms earn less.

This is not wage inequality because these are not equal things. More productive employees are not equal to less productive ones. Productive men are not equal to less productive (article's words not mien) women. If 2 different things are not equal, then there is no inequality.

> Therefore, stronger sorting contributes to widening the gap between high and low earners.

The gap between labor and labor is insignificant compared to the gap between labor and capital.