[quote=@Jbcool]
[@Wraithblade6][@KabenSaal] The point is that a female Astartes would be a male Astartes in all but name. The transformative process would narrow the gap to so close that there'd be no real point in bothering to define male or female.

That's why.
[/quote]

Just my two cents, but this is generally my opinion on the matter. The difference would be so negligible that it wouldn't be worth breaking canon.