I may just make myself sound like a jack$$, but wouldn't adding at flameout only add to aroma? Don't flavoring hops require some actual boiling time (10-30 mins?)
Even at flame out there is enough heat to extract flavor and aroma.
Even if it was just aroma, flavor and aroma are intrinsically linked. Imagine drinking hot chocolate without the ability to smell it as you sipped. Obviously the "total package" would be lacking.