Do not talk about men. I would just like to know why women have more lower body strength than they do in their upper body. Is it because women's' hips tend to be wider because of childbirth? What is the reason?
I cannot find anywhere where there is research showing women have a stronger lower body than upper body. strength is hard to define when comparing it in general. How would one define the strength level of a group of muscles compared to multiple muscle groups(shoulders, chest, back, arms)?
If you want to look at it from a stereotype.... generally women will workout their legs more to have nice legs and a nice butt.. while some think that doing bench presses, etc will make them somehow look like arnold Schwarzenegger. this is more misinformation though and doesnt apply to females as a whole
I ignore the first sentence of your question because it does not make any sense to me in this context (correct me, if I am wrong).
It is quite an interesting question, however, you should back it up with some evidence in the first place. Now, according to the old study (https://link.springer.com/article/10.1007/BF00235103):
The greater gender difference in upper body strength can probably be attributed to the fact that women tend to have a lower proportion of their lean tissue distributed in the upper body. It is difficult to determine the extent to which the larger fibers in men represent a true biological difference rather than a difference in physical activity, but these data suggest that it is largely an innate gender difference.
Answer to your questions was unclear about 30 years ago. And I do not know about any newer theory. But your question seems to be valid at least.
I know this answer is not helping much, so if anyone provides better information, I would gladly delete this answer.