Correct me if I am wrong, but Tecnica, Atomic, and other manufacturers design ski boots specifically for women. It’s difficult to make adult womens boots in a true 21,5: size. Currently companies cannot offer such sizes with an adult toe lug. I am sure small women sizes are under discussion in Austria.
In addition, a lower women’s cuff height has not to do with reduced costs. It’s mostly due to women’s lower calf anatomy. With sizes above ~24.5, a women can easily fit into a mens boot with the higher shell height.
Many women I ski with are currently in 22.5 Atomics Hawx Ultra. They range from 5 to 6.5 in street shoe. Most of these women are kick ass skiers. One has reserved a pair of Atomic STI 110 (unisex) in 22.5 for a Sept/Dec fitting.
Don't know anyone that needed a true 21.5. I am sure there are women/men out there that needed a true 21.5. Just don't know any personally.
I have also watched my fitter put several guy friends in "women" boots because they have shorter lower legs and well developed calves. For me it's whatever fits.
@Near Nyquist is a fitter in the SF area. He is always complaining about the store buyer not bringing in enough 22.5 for the smaller Asian women of that area.
Then there is the technique/skillset issue. A rabbit hole for sure.