The OP article said the same thing, and like this article, it provides no evidence for the statement. I looked for some numbers, and for world bests, men had better performance in every category I found. The study linked below looked at speeds over decades and in every case men had better performance. Both men and women have improved over time, and as a percentage the difference is getting smaller, but in absolute difference it appears the same. It is an admittedly brief search, but I can't find evidence in the form of measured times (not conjecture about estrogen) indicating at all that women perform better in ultra marathons. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3870311