Andy, a good theory but it doesn't hold up to Cinema History. While there is no "official" explanation of the evolution of 3 point lighting, it probably came to Cinema via Portrait Photography practices, which predate Cinematic photography by at least 50 years. Early Orthochromatic film stocks were no more inherently contrasty than modern film stocks; confusion arises because the examples we can now see have been duplicated most often from release prints and not the camera original negative, thus are highly contrasty. The very earliest cinema studios (1897 to about 1905) did not have point-source artificial lighting, such as Arc lights, but were lighted by the Sun and diffused by silks on glass stages. Gradually over the next 20 years, the three point system came into play as Klieg (arc) lights were introduced with Cooper Hewitt Mercury Vapor Lights (flat, blue-rich light source) to offset bad weather and the unpredictability of the Sun as a primary light source. Ortho recorded Caucasian skin tones very dark (not red senstive), so white face makeup (pancake) was used to restore approximate skin tones for Caucasians. The subject is very complex and much more complex than a simple explanation can encompass.
Meh, yet another troll-bait story for the digifan martyrs.