It does. Last year I got a bag of Crisp #19 floor malted maris otter. The first beer I brewed with it was a bitter that came out great and it had an 8 point higher original gravity than the previous version of the recipe using non floor malted m o.
Michigan hop allience went above and beyond what could be expected. Even though I wasn't an actual customer and they wasn't responsible for the repackaged samples I received they sent me some cashmere hops free of charge. They smelled heavenly.
You won't get much effect on flavor using only 5%. The closest that I ever got to the sour tanginess of Guinness was when I cold steeped the roast barley overnight, but left it out at room temperature instead of putting it into the fridge.
It turns out that Michigan hop allience doesn't deal in less than one pound and they don't give away samples. So the ones I got were repackaged by someone who did not properly store them. I should've been suspicious by the non standard amounts in the packs: 1.4 ozs, 2.65 ozs, etc.