The answer has to do with wraparound lighting.
At a recent workshop I was teaching I was interacting with the audience to pose Bec above. This is the image I was able to produce when she looked towards the light. The light was inside a seven foot umbrella, so angling her face made the light wrap around her face. What this did is made the lighting output overall just look more flattering.
Then when her face was facing away from the light, it cast a harder shadow across her face. It creates an almost Rembrandt type of light, but isn’t as flattering as the previous image.
Seems very small right? Yes, but it’s very effective.