If you look at a film like Citizen Kane, for example, you may well be looking at a film where all the cuts were planned in advance. A lot of movies are like that, given the way they are storyboarded. Cuts can be very much planned -- listen to Peter Bogdanovich's explanation of "cutting in the camera" on the Director's Cut of The Last Picture Show.. Or witness the great Bunuel, who used to brag about the fact that he edited
But, on the other hand, not always. One of the best stories in Peter Biskind's gossipy Easy Riders, Raging Bulls: How the Sex-Drugs-and-Rock 'n' Roll Generation Saved Hollywood was how Stephen Spielberg turned in a lot of incomprehensible footage for Jaws that was salvaged by the scissors of Verna Fields. Critics, of course, thought Spielberg was a genius and never mentioned Fields -- who nonetheless won an Oscar.
I defy anyone to show me how you can just look at a film and tell whether the cutting is the work of editor or director.