I also came across this. I dont know where i read it but it is still in my head. I also remember that i just found after that another study that said in the first hours of the plants "day" it would better in terms or repairing damage.
So i am not sure whats true :/
The only way is a real comparison study using scientific protocols. Not a rinky dink exercise like I posted. That was for my own satisfaction and served its purpose to me. It generated discussion. I haven't read your above post in full yet. I'm in the middle of trying to put together a photo essay on a unique trichome situation I noticed during my existing Triangle Dragon run. When I'm finished I plan to come back and absorb your posts info. with a clear mind.
The control that the plant has over the resin in its various forms is remarkable and I would not be the least bit surprised to find that both statements are true. That it repairs, and prevents ultra violet damage. Whether or not the two functions are accomplished by the same form of resin is not a given considering the changes that occur in the final stages starting with the clouding and ending in amber. This is in line with my essay which might clarify the difference in layman's terms , at least the mechanics, of the final stage. I'll drop you a link to it when It's up, hopefully later today..