I don't have any official answers but from a woman's perspective, I find that it is very satisfying to do something RX (at the female weight) rather than feeling like I have to scale. I do scale on some workouts, as I know most of us probably do at some point, but if it were only the one weight I would be scaling 90% of the time in order to keep the same stimulus. I know it's just a matter of semantics, but as someone who has been doing crossfit for several years now and am halfway decent (I'd like to think), I don't expect to ever reach a level where I could do the guys weights and keep the same workout. I'm glad that I don't have to be a games level athlete in order just to do the workout RX. Just my two cents...other ladies might feel differently :)

The Military scales it’s test, so why not scale it here to the opposite sex; not only does it give it a realistic goal to the beginning athlete but it also lets them scale it farther back and not feel incomplete. It Crossfit wanted to take it further, they would scale it farther by considering age and occupation, they could also go as far as scaling it for athletes with prior injuries who are handicapped🤷🏽‍♂‚️

The volume of adult female lungs is typically 10-12% smaller than males with the same height and age.  There are significant body composition differences (men tend to be leaner), hematocrit differences (higher levels of testosterone lead to slightly higher red blood cell counts), and differences in heart size.  Males tend to have a higher proportion of Type II muscle fibers and testosterone while female have more Type I muscle fibers and estrogen.  

As you can see, the machinery is different which will alter the capacity in individuals when all things are equal in training experience, age and height but the gender differs.  Not sure if HQ follows this logic but it is a possible explanation for a gender specific scaling.