It seems that 20% of employees in the private sector are "cadres" and half of them are on "forfait jours". That makes around 10% of the private sector employees working 218 days per year without the 48/44 weekly hour limits. It's more than I thought but I doubt that many of them work more than 10 hours per day. Whether that's "exceptional" or not is a matter of definition, of course.

What do you mean with work more than 10h/day for intellectual work? You don't stop to think the moment you are away from the production machine. And the exact opposite can often happen: you go away from the computer/board/paper/office, make a walk trying to wander at something else as far as you can stear consciousness, and then the solutions/ideas land in your mind.

You’re not wrong but what did the commenter above meant with “50 hours+/week”? Weeks have three times as many hours. Years also have many more than 218 days.

Anyway I found an official survey saying that 40% of them work more than 50 hours per week (but fewer weeks than regular employees) so I guess it’s not so rare (around one private sector employee in twenty).

Used to work 70h/week on average, like every week of the year. I don't think I ever wworked less than 50h in a week