"The worst part is there is hardly any time for resting the mind and body. Our jobs can be mentally and physically demanding."
I don't see how any other "too much" job is excluded; you are blaming the author for his background alone.
For your example: If you have to milk "[n] cows every morning at x o-clock", you are done after n cows every day. If you design large software or manage larger projects, you are done once - when it's done. At least I don't take my physicial work home each day, but when working mentally I do this every day in worst case.
I have done a lot from "both" worlds and honestly don't see much of a difference between aching bones and an aching mind for my private life.