Yeah, depending on how safe they climb, you can gauge their risk averseness. If they are consistently scared about some moves, you can gauge their confidence (which can obviously change over time which might be the best part about climbing). If they consistently pick routes that are too easy or too hard, you can gauge how well they can estimate their own skills.

If they don't care about standard security procedures, they are probably an arrogant person that thinks they know it better ("I don't make mistakes, I don't need to check") and are willing to put their ego before their life (and maybe even the life of others).

If they fail a route, you can gauge how they deal with failures (Easily frustrated? Analysing? Optimistic?). If they succeed at a route, you can gauge how they deal with success (Humble? Arrogant? Outgoing?).

But I think climbing is not special regarding this. This is probably possible in any sport where you're doing dangerous stuff.