The problem with the original statement is that a wall is not a car. If a car at 100 miles per hour hits a stopped car, let’s assume they will both move forward together at about 50 miles per hour.

If the kinetic energy for a car at 50 miles per hour is 1x, at 100 miles per hour, it’s 4x. After the collision, the total kinetic energy is 2x, and the other 2x was absorbed by damaging both cars. That’s different from hitting a wall where all the kinetic energy goes into damaging the car.

The damage from hitting the parked car matches the head-on collision, which starts with 2x kinetic energy and afterwards, it’s zero. (If they are stopped afterwards.)

If the cars were rigid, they would bounce off and go in opposite directions, like balls on a pool table. That would be very bad for anyone inside. Crumple zones absorb energy for good reasons.

I expect that guard rails absorb more energy than a brick wall?