Your telling me that your wrestling, martial arts and "dumb kid in the Army in the 90s" (whatever that means) + whatever sparring, grappling, and real stakes conflicts hasn't afforded you the ability to size up the most dangerous individual among a group of individuals before actually being involved in a fight?
You can't instantly evaluate someone's ape index, their ease and efficiency and suddenness of movement, the athleticism (or not) of their natural gait, their shoulder to hip ratio, their hand/finger/wrist length and size, whether their ears are cauliflowered or their nose is subtly crooked?
I mean...come on. There is no one I know who has been involved in the fight game/martial arts/live sparring or grappling that would say what you just said. That_is_laughable. Its trivial to identify dangerous people before you're forced into a violent confrontation. Trivial.
And the moment a dangerous person with actual striking or grappling prowess squares up against you? No exchange. Just squares up. Its trivial to identify a wrestler who is going to shoot a double leg vs a kickboxer who is going to teep and manage distance vs a BJJ player who looks for a single leg entry away from danger and looks to immediately establish an underhook and wrist control vs most everyone else who has absolutely zero idea of what they're doing (but they're still dangerous because they're still a highly evolved chimp).
If you're telling me that you have no ability to distinguish levels and types of danger in various humans, then I'll take your word for it. But that has absolutely nothing to say about how trained fighters in the real world with a large amount of live sparring distinguish danger and certainly how that would play out in D&D-world where dangerous people are involved in dangerous, life-or-death conflict routinely (and therefore the survivor bias would 100 % select for people with extraordinary ability to distinguish the magnitude and type of danger in front of them).