You're guessing incorrectly.
Link?
Never mind the fact that he has a production company. Or that he always has a project that
he is directing in the pipeline, be it in pre-, production, or post-. They are paid a lot of
money to act in films and the director is the boss. Period. If the director wants to shoot 50
takes, you are going to do 50 takes. They generally only have the actors for three months
max for principal photography. You think they're getting a film made with the lead only on set for
10 hours a week? No.
Clooney might be the busiest guy in Hollywood.