I agree. I don't think the way to increase THC or other cannabinoids is by way of lighting. The plant cannabinoid system is not that well understood to my knowledge. I'm still reading on it though. This link has few sources, but he mentions the same thing. Lot's of cool notes after the first paragraph too. scarring, and such to initiate flower, etc.
http://boards.cannabis.com/threads/factors-influencing-thc-production.201152/
"Resin heads may serve to break up the rays of the sun so that fewer of them strike the leaf surface and raise the temperature."
this, is how I suspect that UV light would react. It may pass the resin heads easier, but that assumes there is some receptor pigment. I don't know of one.