Speak for yourself.
I often work, focused, for 6 hours straight (without any pause). Sometimes, a lot more than that.
Doing what I like, for a product I own, it's totally different.
But, some days, I can't even start to work... And there are days like this that just forcing to start to work it works and I stay focused for a long time.
I guess the article title should be: no company slave can work 8 hours straight. =)