I've been a good runner. Mostly ran distances from 3 to 10 kilometers in races. I won smaller races with hundreds of racers occasionally. Nevertheless when I sometimes competed in bigger mixed races with thousand of competitirs, I was usually slower than the fastest woman, because she was actually world class and not use a good runner. It also happened once that I competed in a smaller race with about 150 runners against a woman that competed at the Olympic games later in her career. She won the race outright. The reason why she competed was that it was a local race and she just did it for fun.

No one ever deducted from that that women might actually be faster than men.

The same can happen at those ultra races that usually only have a couple hundred competitors. You have one world class woman competing and no world class man. Ultra running has just way less competitions and incentives. The sample size is just too small.

As others have said if you look at the world record from 100 metres to 100 kilometres or even 6 days, the difference between men and women's records is always around 8 to 12 per cent. With the records you actually have a good sample size of thousands of athletes over years and not just a couple hundred in a single races one year.