I just tinkered with a couple recipes and the results depend on the recipe. The estimated FG is what's changing. In some cases, it may not change enough to change the displayed est. FG to actually flip a digit, but can make a small change in the derived ABV.
I think this is because it estimates the fermentability of your wort based on the mash temperature, but only when it's set to All-Grain. You can see this if you set it to "all grain," then go to the mash tab. Choose one of the "full body" mashes and then note your ABV. Change it to a "light body" mash and check. Your ABV should have gone up. Repeat with "Partial Mash" and the ABV doesn't change.