How do you define shock then? Because Hitchcock himself has said he wanted to shock audiences with psycho. Craven said the same with last house on the left.
So yeah define shock for me cause we may be on two different wavelengths
Psycho has one of the greatest twists in movie history, but beyond the wittiness it doesn't really have that shock factor. The main advertised character dying early and the Norman Bates being the killer aside, it's a thriller at heart.
"Shock" horror would be like Freddy first appearing with creepy outstretched hands. That old horror movie where the guy looks down at his hand and theirs an eyeball in the center of his palm. The Japanese horror films with torture, the saw series, ect. Movies where the shock/creep value is equal to the scares. You can have a shocking or surprised twist or revelation in a film, but that's separate from shock-horror.