.5F degrees is different from 5 degrees, which is what you based your computation. Also, coral bleaching arises from a multitude of different reasons, the reason of temperature, which you are citing, arises at 30 degrees Celsius. God forbid a tank gets that hot.
http://www.marinebiology.org/coralbleaching.htm (Fact Cite) Also I am not comparing plants to corals. I am comparing organisms to organisms and there is no doubt that "organisms" become stronger and more tolerant to negative variables when exposed to them in a safe fashion like; vaccines, bacteria, viruses, temperature, and predation. I am not stating that you cannot boil a coral, I am suggesting 78 degrees is a arbitrary temperature that was pulled out of the tropical aquarium air when we all begun this hobby and that maintaining that temp within 1 degree at all times may be indicative of an adherence to a improperly vetted theory. Also, the claim we should emulate a natural reef has been the basis of every reef salt company and supplement company for the last decade, do say that it " makes no sense whatsoever" invalidates your own claim considering that the same industry set the arbitrary standard of 78 degrees. Which in function was merely a spin off of the norm set for tropical freshwater fish, where the water is cooler. Also where did the claim that you should increase water temp 5 degrees every ten years come from? I don't mean to abase you, I hope to draw scientific and useful discussion.