So, what do you think happens to the kinetic energy of the kill vehicle? The control model might be based on positioning the kill vehicle in the path of the target, but that doesn’t mean that the kinetic energy of the kill vehicle is not dissipated during the impact.
IIRC physics, it turns into potential energy as it ascends and slows down. It would be the same as throwing a ball into the air, it slows, stops and then picks up speed as it returns to the ground.