I hear this commonly about using the words "male" and "female." I think it's unfair. For one thing, the military uses them frequently, and so would veterans. Another reason is that their meanings are age-agnostic which helps to emphasize the intent of the speaker--to differentiate on sex alone, not sex plus age.

"It's used in the military" supports the point the GP is making, that it sounds unnatural in a common context.

Yes because these descriptions are meant to foster dehumanization and detachment, which is very useful in military and scientific study contexts. That's why they also sound unnatural in casual conversation