It's what I heard for pre-industrial warfare since actual fighting happened so infrequently and most people died from disease than actual warfare.
I tried to make it a direct comparison between the two (the original claim in the Twitter screenshot) not counting disease in preindustry which like you said killed the most men in the military.
Also, none of this has any relevant effect on the fact that orders of magnitude more women have died from child birth than war deaths no matter how you slice it.