That was not prescriptive but descriptive. I don't program every day after work either, but I do sometimes get terribly addicted to a problem and work on it a great deal. I haven't met a good programmer that didn't have it, much like you don't mean someone who's properly good at anything they don't practice a great deal.
> No dentist gets told he gotta setup a practice in his garden shed to practice pulling teeth
This is a weird argument to me, the medical field has an even more unhealthy work/life balance than our field. They absolutely "practice at home" (obviously not through home surgery, but reading and so). Dentists have an easier time than most other medical professions, but every dentist I've met regardless had extremely good work ethic and frequently obsessed over his work.
You can absolutely work 40hrs a week and be a good engineer business-wise. However, most people who are remembered for their contributions to a field (and weren't just in the right place at the right time) dedicated a large part of their life to it. That includes writers, poets, musicians, doctors, anything.. to quote old Onion videos: are tests biased against students who just don't give a shit?