There's a couple of issues.

Men have been running ultra distance since the year dot.

Women have only been running marathons for 40 odd years and it matters.

I think also in coaching of the last 20 years or so, there's been a lot of pressure on coaches, particularly in the western world via the LTAD system, to under work young athletes.

I was once at a North West coaches conference and our speaker advocated Year 9/10 girls train twice a week and if racing only once.
The idea was to allow them to develop and step it up as they matured and strengthened, thereby avoiding burnout.

I knew the coach well and his club.

I asked how many senior women he had in training. I knew it was zero

I can see in the next 20-30 years that women will close the gap from the 10% at endurance events from Half Marathon upwards.
Greater exposure, better training methods to suit them, and greater numbers taking part.