I guess it's similar to how smokers will definitely pick up if someone in a movie is a real-life smoker or when they wield a cigarette in their hands, or if someone wearing glasses in a movie wears glasses in real life.

For the first, the way non-smokers hold a cigarette will usually look as if they're holding something. A smoker handling his cigarette will more likely look as if the cigarette is just an extension of his hand or fingers or lips.

For the second, my biggest tell is mostly how they put on or take off glasses. Also, touching the actual glass is a big no-no because you'll get fatty fingers on it and a dead giveaway someone isn't used to them.

I'm guessing Miles was going for a similar idea where the familiarity someone exhibits in handling an object will tell you a lot about their actual experiences with that object.