Clint Eastwood is many things: actor, producer, director, musician. One thing he most definitely is not is an intellectual. Not that he is not intelligent, but he himself has often said he relies on his "gut" when it comes to making motion pictures. The people at Cahiers du Cinema apparently did not get the memo. For them , Eastwood is an artist of the highest order whose films are filled with metaphors, symbols, hidden truths and deep meaning. Isn't it enough to say he is a great filmmaker, an icon?
And by relying on his "gut", I assume Clint is saying that he spent many years learning and developing his cinematographic skills and now he knows by heart and experience what it works and it doesn't for him. By "it" I am talking about cinematographic language such as metaphors, symbols, meanings, camera shots/angles/movement, mise en scene, etc. (Since I didn't read the book) maybe that is what the people at Cashiers du Cinema are talking about and this is their way of describing Clint as a great filmmaker.
As a theme, it is best described as that which returns or always tries to return to the projections of our imagination or memory...."
That is one of the focal point of art, movies included.