I can see the gap closing, but I don't know if women become better than men.
There's a good book called Born To Run about ultra runners and offroad runners etc, though it's a long time since I read it. There was one person that the author kept going on about, a US female who was apparently really good at running down hill and could do it better than most men. But she wasn't winning races, just very competitive in that part of it.
I think women carry less muscle and weight. A small frame is better in endurance, whereas muscle and power is better for sprints and middle distance. So there's less of a gap and women are more competitive with males.
But world records in all distances are still quicker for males than females.
https://en.wikipedia.org/wiki/Ultramarathon