Absolute rubbish, no such thing as a "flutter valve" in the Honda exhaust system.
You are being conned.
Not saying there is anything wrong with the Akra, I love them, still one of the kings of quality, but you are being told complete rubbish.
Buy the Akra if you like it and can afford it but there are plenty of option and good quality ones for half to two thirds the price.
I especially would not buy anything from someones you told such rubbish to make a sale.
I have Akras on my KTM, had them on my GS, my zx14, but Ive just put a carbon Leo on the CT and was surprised at how very nice it is for half the cost.