@snibgo I may have read some of that at some point. Good to see it all in one place.
@PhotoPhysicsGuy I called it an I line in the other post. Has its history in tv signals and colour spaces as far as I know. I am confused by your use of the term saturation line. Saturation increases with distance from the centre.
It is because of their attention to detail that the skin tones are good. It comes down to the experience of the video, lighting and makeup crews. The industry is really good at coordinating and visioning from beginning to end. You should watch the The Mandalorian video I shared a while back. The technical, creative and leadership prowess of these people are something.