Women, even in developed countries, are still much less likely to be a part of military or paramilitary groups or engaged in hostilities during wartime. Essentially, if you kill 100 men, it’s easier to claim “A lot of them were paramilitaries, honest!”; if you kill 100 women, that line becomes statistically unlikely; if you kill 100 women 20 times in a row, it begins to paint a very gruesome picture.