If those engineers are working 40 hours a week and are awake for about 110, what are they doing with their other 70 hours? Sure some of that is commuting, showering, etc., but presumably they have other activities.
For some people, their hobby is technical writing.
Saying that they are mutually exclusive would be like saying that being an engineer and doing puzzles is mutually exclusive because they both require a lot of mental effort.
Or being an engineer and a musician are mutually exclusive. It's a silly thing to assume that technical writing is somehow different from any other hobby.
Writing great blog or having pet project after working full time is equivalent of working overtime or crunch. Had this been effective, persistent overtime would be effective too.
Which is why it is not happening. The actual rest time and hobby is when you do it whenever you feel like and stop how you feel like. Once you make it project and treat it seriously, it is work.
Also, other stuff that is done after work: cooking, cleaning, shopping, picking up kids and talking with them, sport to be healthy. These amount to not exactly small chunk of time.
For some people, their hobby is technical writing.
Saying that they are mutually exclusive would be like saying that being an engineer and doing puzzles is mutually exclusive because they both require a lot of mental effort.
Or being an engineer and a musician are mutually exclusive. It's a silly thing to assume that technical writing is somehow different from any other hobby.