There's no black and white language on this though. The brain is composed of parts that sort of compete and work differently. A simplistic view might say you have a rational brain that thinks in terms of logic and facts. There's another, intuitive or emotional, that detects patterns in raw data from the senses, makes approximate models of the world, and triggers instinctive responses when seeing them again. This is the part of the brain that pulls your hand off the stove before you've recognized it's burning. This is how soldiers have described being compelled to dive to the ground for no reason just before a bullet hits where the head was. An input comes in, matches a model, a response is selected, it's activated, and this all happens in an instant.

That intuitive part of the brain represents the vast majority of what we do day to day. Our rational brains activity feeds into it, too. However, cues about people's speech, behavior, emotions... these are naturally all picked up best by the emotional brain. Jessica may have been doing what Paul describes for much of her life with that part of her brain soaking in details she can logically spot and some that are unconscious impressions/feelings. Trial, error, and external observation correct inaccuracies over time if one lets them. At some point, the models in her mind were honed so well that they can spot significant positive or negative traits very reliably.

So, there's nothing wrong with Paul's description and it's likely Jessica couldn't fully explain her mental model because she doesn't know it. She will certainly, with introspection, have elaborated out many specifics that she could explain and you could train yourself to work with. However, as I said, this is mostly a subconscious process that can at best only be partly elaborated. Like any black box, you can only assess its reliability by looking at the quality of outputs that come from inputs.

There will always be false negatives, false positives, and occasionally WTH!?'s from intuitive decisions about people. What's good in this space is quality of results whose accuracy is consistently good with relatively-low, error rate. Paul's statements indicate her emotional/intuitive brain uses very-effective models of people far as their character goes. The results speak for themselves. That's all you should need.

Note: Only way to learn such skills is experience. A job where you deal with lots of people in ways that makes their ethics show can accelerate the process. Still takes years and years, though.