The difference is this:
Trait: He likes to play sports.
Motivations could be that he is concerned with health and fitness, he is concerned with being part of a group, he likes the socialization and "team spirit" part of sports, he's very competitive, etc.
So just playing sports is a trait. But if you know someone better, you probably have some idea of *why* he likes sports. *Why* he plays sports will tell what he values. The fact that he plays sports isn't enough to go on.
You might have to ask questions. But yes it's still observing people, it's just moving past observing behaviors to observing motivations for behaviors. You do have to make a bit of a leap in guessing the motivations sometimes, and obviously that can cause errors in typings. But hopefully people keep their typings fluid enough that as more information becomes available, they will adjust their typings to make them more accurate.