It's about putting in effort for things you want to do vs things you are told you need to do. Kouhai-chan didn't see the difference - no wonder, as in school there really isn't one - between these, but Ishii clearly does. Helping out the community, spending time with friends and family; those are the things that he wants to put effort in, so he does, he 'works hard' there. Grinding 9 to 5, especially in a Japanese company, only for money, is something that is told to him that he needs to 'work hard' at, so he doesn't. That's why Maruyama tells him he didn't change at all in the extras - he sees the difference the kouhai can't.