These academics obviously haven't had much experience with farm people even today, or with women from pastoral societies for that matter. This shouldn't have been such a surprise to them.
Everywhere I've been in Europe where things still haven't changed so much you see women on farms working in the fields, forking and bailing hay, carrying huge loads, and on and on. On top of that they have to give birth to and raise multiple children. They not sitting around eating bon-bons and watching soaps.
My mother, who was 5'6" tall but only weighed 112 pounds and looked as if the wind would blow her away was stronger than most men from working on her uncle's farm after her mother died.
Maybe it's because I know a lot about life before 1960, but none of this is a surprise to me. Women didn't have to go to a gym to get muscles.
These were in 1950 believe it or not. There are lovely folk songs about it but it was back breaking work cleaning those clothes. My grandmother said you'd be bent over like that for the whole day. When it was over you could barely stand.
They did dangerous things too.
Don't get me wrong. The men worked like mules too, but the women had the added burden of child bearing in a time before modern medicine. My father's eldest sister (by 14 years) died in childbirth at 19. Nobody in the family every got over it.
It wasn't any better in hunter-gatherer societies from what I can see. In fact, maybe the disparity between men and women was even greater. Just look at the life-style of the Indian tribes in the American southwest. The women set up the tee-pees, or yurts, or whatever, did the foraging, ground the corn if they had any, did all the cooking, scraped the hides to make clothes, minded the children, and then packed everything up and had to trudge endless miles with babies at the breast and toddlers tugging on their skirts. In the middle of all that they had to be sexually available at all times. From what I've read, when the men weren't hunting or raiding other villages they were mainly sitting around telling stories. The grunt work fell to the women.
There was a reason why my grandmother told me that each time she was pregnant (twelve times in all) she prayed it would be a boy. That's also why education was the all consuming goal for all her children: so that they didn't have to do that.