First of all, this is an article written by someone who has never worked in academia. The stress varies quite a bit. Are we talking about at PI in a science lab who is also teaching courses and supervising a large staff? An assistant professor at a SLAC with a baby at home? There is no such thing as a typical professor.
The idea of summers and winter breaks off would be a nice one, but that is prime research real estate. We are not elementary school teachers.
The idea of leaving one's work in the office is also somewhat unrealistic. The office is one's brain, and it is very hard to turn that off.
The article shows no conception of academic politics, which makes the job very stressful. Not in my case, fortunately, but for many, many people.
There is one, and only one grain of truth in this article. The autonomy of being a professor makes it a great job. Being able to determine the course of one's own research. In some cases, a very wide latitude in course content as well. For me, but not for everyone.
So, yes, for me, middle-aged white full professor at research institution surrounded by very nice colleagues, the job is non-stressful. I am ambitious so I do more than I have to do to earn my salary. I am working for reputation outside my university more than for the salary itself. This added work is not stress-inducing, because it stems from my autonomy. We know that the three key ingredients for happiness are relatedness, competence, and autonomy. Academia can score high in the second two (not always) and in the 1st if you are extremely lucky.
I view the number of hours worked as somewhat of a distraction. I could work more hours and get less done. I happen to be faster at any given task than most people. If I were also efficient about the small stuff, I could work even less.