Nothing proven about the UV, but I have my Diamonds in an aviary and they sit in the sun from sun up till about 1pm every day.
I had coastal outside and they never sun baked, only came out at night.
The Diamonds do seem to desire the suns rays & benfit from it.
The largest of my females statred showing strange behaviour patterns and some signs of illness untill I moved her outside (I thought she was going to die). Now she is now strong healthy and shows no sight of the strange behaviour or illness. She is about 7 years old, about the time that DPS would start showing. Highly recommended that you give her more natural light.
But then again I have know people to keep them inside without Fake UV light and not have a problem with them for over 20 years.
So who really knows what they need, it seems they do beifit from the suns light.