I think you were a little harsher than necessary, but this is a good point. Surgeons aren't doing surgery 40 hours a week. They'd be making tons of mistakes if they did that and they'd be getting burned out. The last surgery I had the doc only did ops on Tuesdays and Fridays.

In many ways it's a good analogy to writing code 40 hours a week. It takes high concentration and the quality of output drops heavily when you're tired or need a break or rest.