Rear Bumper Cover Query

[staudi17]

Hi, hoping someone can help. I have a 2017 Audi A3 Saloon and was cleaning it today and noticed theres a hole under the rear bumper and wondering if it is by design or if there is a part missing. The wiring for the rear parking sensors are exposed up inside the hole which makes me think I am missing a part here.

Attaching an image of a similar bumper, see the large rectangular hole in the middle of the bumper towards the bottom, hoping someone can tell me if there should be something here to cover that or if that is by design?

Thanks