Whose side are you on?

This "attitude" you're talking about is really a poor assumption. If anything, he's being efficient with his time, which is something that would actually help him down the road. What he did here was actually seek clarification of expectations, then acted accordingly. That's a good trait.

I never once had a teacher get on my case about skipping a homework assignment if it was optional. No hard feelings and it never caused any issue with work for me in my 30 years in the workforce.
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.