This feature works really well for me. I have an ice chest mash tun at 9 lbs and a keggle that I occasionally mash with at 30 lbs. I hit temp pretty spot-on with this adjustment. The rule of thumb though is to make sure you keep your grain and tun in the same room overnight, especially in the winter time. Also, never just go by the strike temp on the recipe that drops in there when you select your mash profile. Always use the strike temp calculator to get a more accurate measurement that takes current temps into consideration. I've been using beersmith for over a year now and this has been my experience with some of the nuances of the software.
Not all chemicals are bad. Without chemicals such as hydrogen and oxygen, for example, there would be no way to make water, a vital ingredient in beer.