Very informative Retro. 
As for the why?? Good question.  I guess I got caught up in the hype and started experimenting.  This is all a learning curve to me. The good part is that it is easily reversed

Apologies if I come across a bit condescending.. its not my intention but its an issue we have in the sign trade also.. materials not designed for LED having lots of them placed behind.
You can try placing a sheet of deep opal acrylic behind the translate as that will diffuse the light more..and / or taking some of the GI LED out to lessen the amount of light.
Ive seen people in the sign trade blob clear silicon over LED strip to act as a diffuser and it does actually work quite well.
There is a new type of acrylic on the market for backlit letters... it has a speckle inside it to bounce the light around more. More than likely, future translites will be made from this new material.. but it aint cheap...yet!