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.
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
Keep in mind that not everyone on the internet uses English as their first language and they might use words weirdly cause it resembles what they're used to
