I mostly agree with the author, but I don't see the point of stopping yourself when you're "in the zone". Why lose the flexibility?
What works for me is having a baseline of 3 or 4 hours of daily work, and not imposing any hard limits when I want or need to do extra hours. This works out great, because I have no excuses not to do the boring routine work as it's just a few hours, but I also have the liberty of doing obsessive 10h sessions when I'm trying to solve a tough problem or when I'm working on something fun.
I'm currently experimenting with a very long kata (tens of hours) where I do 1 pomodoro a day (although I frequently miss a day, and occasionally do 2 pomodoros in a day). What I have found fascinating is that stopping early keeps my interest up for the project. I "feel like" working on the code every single day and only miss days due to illness or other unavoidable circumstances.
There is something to be said for always leaving yourself wanting to do a bit more. Never being satisfied means that you are always hungry for more.
It probably depends on the person. When I do what you are suggesting, I seem to burn through too much "cognitive resources", getting a ton done, then crashing into a haze for a few days to more than a week. At that point it's hard to get started again. So I see the advantage - for some people - of cutting "in the zone" time short.
I should note that "in the zone" time for me can last a few weeks. Most recently, a long one came after spending a lot of time at the gym doing cardio. When I hit "the zone", I stopped going to the gym and just worked. Now I'm in the "haze phase". The problem with the haze phase is it's hard to focus on anything, including going back to the gym, which should theoretically spur another "in the zone" phase.
The author thinks in the long run the 10h sessions hurt you. They acknowledge specifically that got a week long exercise more work will produce more results but that they feel their average productivity is much higher over months or years by never getting bogged down even when they're making progress.
The 3 hours every day pattern might work for the author and many other people but it won't work for everyone. That's the problem with generalizing. There's no one size fits all solution for an optimal work schedule.
I think the lesson to learn from this is that we should work harder to not only remove the stigma of unusual work schedules, but encourage them so people can discover their maximum productivity schedule for themselves.
What works for me is having a baseline of 3 or 4 hours of daily work, and not imposing any hard limits when I want or need to do extra hours. This works out great, because I have no excuses not to do the boring routine work as it's just a few hours, but I also have the liberty of doing obsessive 10h sessions when I'm trying to solve a tough problem or when I'm working on something fun.