Thanks for the link. Seems like some people are saying it's now a virtual AI-assisted proximity sensor, run by the software, and that there is no physical proximity sensor. Others think that's nuts and that it's still a physical sensor.
While on a call, I just tested by holding the device away from my face and gradually sliding my finger across the top of the phone covering more and more space on the top. As soon as I covered the space between the camera and the wifi symbol, the phone shuts off. I slide my finger back a little bit, it turns on. Obviously the sensor is just to the right of the camera. I must be holding the phone away from my ear or something, it seems like it's working properly when I test it the way I described. If it continues I'll just factory reset and try again and see.