You can easily estimate the time required to perform some physical tasks. It's a bit different if you're working on something you never did before, but again as an electrician or carpenter this rarely happens after the training period. Working more hours generally does result in more work done, although the physical factor makes this work-life balance waaay more obvious to whoever is working.
In IT I'm constantly working on things which are slightly different than before. Time estimation is big common issue in the field. I'll be fully honest and say that working 4 or 8 hours a day makes absolutely no difference in work being done for me, except in very rare cases. Dedication has nothing to do with it (I love what I do). Technically I'm not stopping to work at the 6pm hour mark, my brain keeps thinking about technical issues also during off hours and the weekend.
I don't know about you but I felt physically tired, but satisfied at the end of the day when working as a carpenter. Sense of accomplishment was much more rewarding. When coming home I would enjoy something different. The next day I was recharged.
When working on problem-solving, I don't feel physically tired, but I can still feel exhausted in a way that prevents me doing other things. It's much, much harder to find a good balance. And I'd stress this again: putting more working hours sitting in front screen is not necessarily achieving anything.
Note also that these crazy perks as outlined in the article are not my experience in IT working in several places in EU. Yes, our working hours are more flexible due to the nature of the job, but I've yet to see such entitlement in my career. Maybe I've been unlucky.