The change in fermentability w/ change in mash temp is highly dependent on your base malt.
IME I haven't been able to significantly reduce fermentability (via high mash temp) on beers made with an American 2-row base. The DP is off the charts. Its bread to produce extremely fermentable worts, even with rice and corn.
Moral of the story - for various grists, don't expect the same change in fermentability with the same change in mash temp. Don't just select a "Mash Profile" in Beer Smith and move on - dive into the mash procedure, make sure you're temps, thickness, volumes, etc. are consistent. I don't even use the "Mash Profile" option for this reason.