I don't think that really applies to the Imperium though since you have to remember that the vast majority of Imperial words aren't on the front lines and just go along shipping off men and materiel to the places that do need it.
I'm afraid the same rationale also applies to an industrial workforce.
Take the modern West for example; inducting women into the labour force en masse is one of the larger factors that has led to our loss of replacement birth rates.
For a machine hell-bent on optimizing it's capacity for industry and war, optimizing sex roles is the only way to perpetuate a cycle that necessitates a constant loss of human life, short of using some scifi contrivance to handwave away human biology.
Even if disregarding essentially biologically ingrained sex roles makes for a larger short term conscription, the end result is that over these thousand-year spanning space wars, your front line manpower reserve gets worn down to nothing, because you have gotten all your women killed marching them over a minefield to clear a path for the tanks.
That and call me a curmudgeon, but without the degree of distance that a woman being an actual space-alien of another species, or an indoctrinated religious fanatic operating under a contrived set of restrictions, and heavily compensated by being overequipped, and absurdly strict, putting "normal women" on the battlefield, doesn't look heroic or cool.
It looks desperate, sad, lame and contrived.
Normal men are expected to fight, and if need be, die.
When the women are expected to do the same, then it's a sign of immanent failure, preceding rape and despoilment.
You can't have a "clean" war with normal women on the battlefield.
And it ruins the aesthetics of a game, because you can either ignore the woman-ness of the woman, thus at best getting an incongruous "Ellen Ripley" which is fine in moderation, but becomes weird when every other women is Ripley, or you can play on it for drama, which isn't what we're here for.
We're here to kitbash trukks, and make little plastic blokes die, not explore social justice issues through the lens of a game of plastic soldiers set in a fictional setting that is a shitty place on purpose, for the facilitation of imaginary pitched battles.
At my LGS Frostgrave kits sold like hotcakes; everybody loved them for kitbash fodder, or for the game itself.
But long after all the male kits were sold, and to this day, there's still an unsold pile of woman warriors gathering dust on a shelf.
The battlefield is no place for a normal woman, and every normal man knows it's his job to keep them as far away from one as possible.
