My read of the study is that it more or less proves the opposite: the wage gap is the result of women having such powerfully different preferences that it shows up even when we know discrimination is impossible.

So location, work experience, and driving speed are gender biased? Those are all free choices which depend entirely on the driver. As others have noted, women tend to earn more from tips in general, which are poorly represented in this study. So women will actually earn more than the study has indicated, and claims to have fully identified with those three points. Thus women actually appear to probably earn at the very least their fair share - or perhaps even more - when tips are taken into account.