A pillar of the success seen with double threshold is simply the very large number of miles, and high quality aerobic miles you put in. With a few exceptions, though this number is growing (thank goodness), many women just don’t run the total # of miles needed. You get some who do: Seidel, Shalane, and they rise to the top.
From a young age in the US, girls are given much less in terms of training load, and often ridiculously low mileage. They are fed the idea of “you can’t run as much as the boys” from a young age. But to paraphrase Renato Canova, everybody in the marathon’s gotta run 26.2 miles.
Obviously women’s bodies have more factors at play to what they can physically handle, but I’ve always thought that if more women just got rid of the mental block around more mileage, we’d start seeing a lot faster times and depth from them. I think it’s finally happening now.