I think their point is that a simple infra red sensor like outdoor motion detector lights will do what you need. There's zero need for a camera to do this. Massive, massive overkill.
There have been significant price drops in small modules for short range, rudimentary V-band (60 GHz) radar to do this sort of thing, which companies can built into their consumer-priced product.
I think some of the better ones are a little bit too power hungry to be entirely wireless on battery, and have a USB-C port in their rear, you're meant to plug it in persistently to a small USB charger and tuck the cable away somewhere.
This seems to be the first instance I can think of where a vendor is trying to take a middle road of extracting more value from a camera while also having a more conservative view on privacy. We'll need to see exactly what that means in practice, but I'm glad someone is finally broaching the question.
That's like saying that you don't need a whole PC to do local AI inference because it can run entirely on GPU. The point is that the lights example is just the beginning.