I haven't looked into this in great detail, but I have seen this study discussed elsewhere, and I think there's at least one point worth making.
I think a lot of people read "sexual dimorphism" and think binary gender, by which I mean something like a very hard separation between biologically male and female persons. But even in this study there's an enormous amount of overlap, which is obvious from the standard deviations in table 2:
If you assume a normal distribution (the authors do; they use a t-test for example) the curves would look like this:
(note: I borrowed this graphic from The Society Pages
Mostly, I think the "biology" vs "social construction" debate is a red herring. There are people who adhere ideologically to strict social constructionist accounts of gender -- probably in large part for political reasons -- and results like these certainly challenge that ideology. So fair enough as far as that goes. I don't think an absolute social constructionism is a tenable position, but it's also not a mainstream position in the social sciences.
However, I say it's a red herring because acknowledging that physiological differences exist doesn't actually tell you much about some of the sociologically interesting facets of the gender wage gap. Physiological difference may partially explain differences in occupational preference, which is one of the biggest components of the wage gap, but it won't explain why we value traditionally masculine occupations more than traditionally feminine ones. In other words, it may tell you something about occupational sorting but not why occupational sorting creates a gap in wages.
Nor does it explain why there is a fatherhood bonus and a motherhood penalty which don't reduce neatly to differences in time taken off work. Nor can physiological difference ground an account of why the wage gap declined so dramatically during the 1980s. All of these quite obviously involve sociological dynamics. One can acknowledge that biological difference exists and also embrace a political/ethical perspective which calls for cultural change. I think one should also be careful not to fall into overly simplistic essentialisms about biological determinism which aren't really justified by studies like this one, as per above. It's all rather complicated...