Ah, so you misunderstood the post then, I think.
No, I understood where the OP was going with their thoughts on the matter- giving a possible modern scientific explanation as to why the astartes process only works on males.
But, this is not modern science. We already know that the Emperor's own male genecode, warpcraft, and all sorts of voodoo was thoroughly tangled up in the creation of the Primarchs and, subsequently, their Legions.
My point was why do we really need a detailed explanation? Why does this particular bit of lore have to be explained above and beyond
the already numerous references in the lore that it simply doesn't work on females?
Basically because in a universe of daemons, basically magic, and incredibly advanced medical science that is basically magic, it seems odd that women are singled out of the Space Marine club.
With all that went into the making of the primarchs and space marines, seems odd to cut your recruiting pool in half.
Compared to the rest of the universe, it seems like it requires a reader to suspend their disbelief a bit.
Which I do, but it's still something odd.
If you look at it as a numbers game and in breeding terms, not in a society bound by political correctness, it actually makes logical sense to limit it to males only.
You are looking to create the perfect warrior- strong, highly physical, highly aggressive. Traits that are, as a whole, naturally higher in human males. This is a simple biological fact. Not to mention that adding testosterone to a 'normal' woman to meet the same natural level found in a male causes all sorts of issues biologically.
Because of how human reproduction works, a healthy population can stand to lose more males and still remain viable to recoup the loss suffered in a much shorter
time than if it lost the same number of females.