Well, if someone has learned from dots or, almost as bad, a single recorded source, they are far more likely to carry the conviction that they have it right and don't have to listen. That's my experience from playing in mixed sessions for over 20 years. I could even go so far as to claim that I can tell from someone's playing whether they learned it from dots. Less so in the case of long-seasoned musicians who have learned mostly by ear in the past. They are the only people who can afford to pick the odd tune up from dots out of expedience. The only time I ever look at dots is as a last resort if I can't make out some twiddly bit of a fast tune, as you were saying. Even then, it's better to seek out another version in order to construct your own work-round.