The fact that they own the device? From the article it’s implied that the doctor wasn’t recording.

That’s the thing though, it’s multiple levels of trust required. Point is the device is connected to his phone, You don’t just have to trust the doctor not to hit the button to record (either intentionally or accidentally) but you also have to trust facebook not to have set the device to do some stealth recording outside of permission (again either intentionally or some sort of “accidental” system). Or also cyber attacks (IE doctors phone or glasses could have been infected by a virus that quietly enables the camera and sends the footage to some shady extra site). The presence of a cloud capable camera adds multiple layers of issues, beyond just the owner of the camera itself.