The things he does, in the flash, would make the engine capable of getting better fuel mileiage. If you were stuck on a road where the speed limit was 55, you would see numbers in the 50's, no problem. I've seen 65 on his flash, with my concours 14. But, to do that, you can't do 70mph....50-55 is it.
At higher speeds, we have so much wind resistance to overcome the only way you will change mileiage much is to streamline the bike. If a person did that, 100mpg would be possible, and probably more, but until we do that, were stuck right where we are..
The real reason for the flash is the response, and control.