Claim seems to be based exclusively on data from UK (and I can't help being skeptical of its accuracy), but it's pretty clear the pattern has historically tended in the opposite direction around the world across traditional societies, where violent casualties are more often male
Pattern is pretty clear-cut across hunter-gatherer societies https://quillette.com/2018/02/24/behavioral-ecology-male-violence/ https://twitter.com/Evolving_Moloch/status/942096199246536704