After a big splash on the launch we haven't heard a thing about it since. When manufacturers make claims like this I would definitely ask for the back up data to prove it. If you mean converting a single car garage to a two car garage it might make some sense. However, adding a second building to the property is a much bigger project that would be very hard for you to recoup. If you are talking about the second building, you might as well take it one step further and consider including a home office, workshop, or another room you can use.
Some home improvements provide a great return of investment.
Others have the same value as a losing lottery ticket. Generally improvements that are very personal in nature like pink walls, velvet wallpaper, etc., will have a negative effect on value. But improvements that add to the physical real estate of your home will increase value. Some of the top improvements to consider would be kitchens, baths, basements, replacement windows and other room additions. Things like adding a Jacuzzi to a house whose walls are cracked or adding an addition that doubles the size of your house would be foolish for obvious reasons.