City Safety tested?

Hi together, I mean I read something about this topic here in the forum a long time ago, but can’t find it about the Sufu. We recently got a new flat-screen TV, packed in a huge cardboard box. So I finally thought of a way to demonstrate to my neighbor City Safety. Box placed at the end of our turning hammer, City Safety active, speed approx. 12 km/h, no hand on the steering wheel, no foot on the pedals and… boom, cardboard scrap. Penetrating. Does City Safety only react on metal or why didn’t the system trigger? Car is an XC60, MJ10. Greetings Michael