Here's my attempt to answer some of the questions in this thread.
I've brought quite a few anemones through bleaching myself. I've lost my fair share as well.
Once an anemone bleaches, it's ability to obtain energy and nutrients is drastically reduced. Such an anemone is highly likely to succumb to nutritional deficiencies. Despite the best efforts of the hobbyist. The faster the anemone can rebuild its zooxanthellae population, the greater its odds of survival. IF this new product contains viable zooxanthellae, and its of a clade the particular anemone is able to utilize, it may be beneficial.
I have brought a M. doreensis through bleaching while feeding it zooxanthellae from a healthy M. doreensis. A similar experiment was done on S. gigantea with apparent success.
The florescent colors, or "pretty" colors, are produced by the animal itself. Zooxanthellae are a golden brown color.
It's not speculation that corals and anemones obtain zooxanthellae from the surrounding water. Many corals and anemones begin life with no zooxanthellae. The only way they can obtain zooxanthellae is to take it from the surrounding water.
Corals and anemones are constantly regulating the population of zooxanthellae within their tissues. As the population grows, they must discharge a portion to maintain a relatively constant population. This means that in a well stocked mixed reef tank, there may be multiple clades of zooxanthellae floating around in the water. This also means that an anemone could totally bleach, lose every zooxanthellae in its tissues, and still recover in our closed systems by obtaining zooxanthellae from the water. Even if we never add zooxanthellae to the system. This doesn't guarantee a recovery though.
HTH
Peace
EC