What I'm seeing, over and over, is that this drive to "work hard" ends up creating all kinds of "bad" work; difficult/tedious labor intensive decisions rather than efficient and innovative ways that are objectively better.
He gets stuck on a problem, and won't put it down and go pick up the other problems that are easier to complete and provide similar (if slightly reduced) value to the customer. That's his "hard work" ethic at play, and I've found it pretty difficult to break him of that habit.
And this isn't some idle efficiency meddling on my behalf; instead of providing some incremental value on a daily or near-daily basis, he goes completely dark for days or even weeks at a time before surfacing with a "glorious solution" to the problem he's ratholed on. If he had dropped the work at the first sign of trouble (seemingly anathema to a "hard worker"), he would have found other ways to have an impact on our customers. He's substantially less effective because he wants to "work hard".
I do believe that people who value "hard work" generally don't understand this downside, and it's kind of fascinating to me, because of how ingrained this flawed trait is into an entire subset of American culture (being an American myself).