I haven't tried it myself, but I believe the OC is referring to the webcam USB mode that Pixels (idk if this is an Android feature or a "Pixel" feature) have. To enable it, connect over USB then you'll have a notification along the lines of "Charging this device over USB".
If you click that notification it'll let you enable Webcam over USB mode, which I assume just causes the phone to act as any other webcam device would.
I've been using droidcamx to utilise any android phone as a webcam for a couple of years and it's working great.
Phones tend to have way better cameras compared to webcams so the video quality will be top notch in must most cases.
It's cool they included this into android 14, though.