I would think the side of the seat is more susceptible to the type wear like in your pics because regardless if you think you are or are not, you a rubbing against that every time you enter and exit the car. All you are doing on the seat cushion is sitting down on it. The side is also raised up leading to you hitting it harder.
Good for you if they replace it, but that seems like some good ol' wear and tear on a car that is now over 3 years old.
Good for you if they replace it, but that seems like some good ol' wear and tear on a car that is now over 3 years old.