Revealing mistake: As a homage to the original; when Norman carries Marion's dead body, wrapped in the shower curtain to the car, you can see her bra strap through the curtain.
Revealing mistake: When Norman Bates is wrapping up Marion's body in the shower curtain, you can see her feet sticking out. Just before he goes to lift her body, she puts her feet together.
Revealing mistake: In the stabbing scenes of both Marion Crane and Arbogast, as the knife is withdrawn repeatedly, the knife always stays clean and does not receive any blood on it.
Revealing mistake: When Norman is dragging Marion from the bathroom, she is moving her head although she's supposed to be dead.
Answer: What is shown is what you would see in the rearview mirror. Being in the mirror, it's a reverse image. Think about if you were looking at the cars pulled over head on/facing the driver, the road and the driver would be on your right. Shots in the mirror though shows the road and the driver on your left, the reverse.
Bishop73