The impression I get from those tweets is that it’s not making the eye look as it it’s always looking at the camera, it’s just adjusting so that if you look at

The impression I get from those tweets is that it’s not making the eye look as it it’s always looking at the camera, it’s just adjusting so that if you look at the screen (the persons eyes in e.g. FaceTime) it looks like you are looking at the camera. So if you break eye contact with the image of the person on the screen, it will show you breaking eye contact in your video.