Studies has shown that unstructured conversations has 0 correlation with on the job skills, if you just ask questions and go with the flow of the conversation it is extremely unlikely that you actually learned something important.

More likely is that you got biased from that conversation and that bias colors your later evaluations of them. A lot of people are biased like that, studies shows that, maybe you are one of the very few that would be the exception of these studies, but it is unlikely, much more likely you are among the large majority who overestimate how well they can read people in free form conversations.