That's probably true for typical people. There are exceptions like John Carmack and Jon Blow, who can code for 10-12 hours a day and who are running a mini-crusade on Twitter against generalizations like that. In general, I think you're right though - if you're such exception, it should be fairly obvious to you that you're exceptional in this regard and the rule does not apply to you.
But he was also a terrible manager, as he was thinking/expecting the rest of the world to be as performant as he was.
One of my greatest friends and associates lives for life itself.
When we first collaborated on a project I had gotten a head start on it and was investing crazy hours.
As if it were the rule, I burnt out after the core implementation was done.
That's when his super powers kicked in.
While I had been toiling and feeling like a solo dev for my "heroic" commitment, he had been intimately learning my code and was fresh to build all the required features on top.
I learned a really valuable lesson about the nature of teamwork. To this day, if someone slightly lifts a finger or sounds the quietest of utterances, they're still doing more than I should ever expect.
Still they probably have idle time too that really defines those moments of N days at 10-12 hours.
They probably live a way that Bertrand Russel would approve of.
I strongly doubt that either Carmack or Blow are told by management to work 10-12 hours/day. That they feel like doing it is another matter.