I don't think it's a poor assumption given the way he described it. He said it was "long and annoying" and he was busy with "other things." The story also started out with "If you don't want me to take advantage of your grading policy..." I think one doesn't need to assume that he has a very blase' attitude about it. Maybe if he'd elaborated about what else was so pressing that he didn't have time or he hadn't said that it was annoying then I wouldn't feel like he had a bad attitude.