Yes, well this is exactly my knee jerk reaction.
But take the study on its own terms and assume for a moment that you view the evidence in the most favorable light against the party whom you just delivered summary judgment against assuming that all the facts as presented by the researcher are established and drawing all reasonable references from those facts. Starting from here the evidence is that wealth distribution can be found to obey the models of statistical mechanics and specifically the model of the Gibbs distribution at least in Japan, the U.S., the U.K., India, and 19th century Europe. If this is so even for a few societies and for a limited amount of time, what does this say about the structure of human societies and/or power distribution within human societies? This is the limited question.
It is possible that it is a coincidence that the Gibbs distribution and wealth distribution correlate, but even so it is a strange correlation even for a few societies.
But a bigger _if_.... If it is so also true for societies that don't have market systems what would this say about the structure of complex societies in general? (Maybe you should leave out my "bigger" ifs.... )
Jerry