Well that's going to be real nice here in dead of winter and a/c turns on.
The AUTO temperature control will turn on whatever is needed to try to achieve the set temperature. A closed car this time of year will likely be warmer than you want, even though the outside temperature may be comfortable. Come winter-time, it will turn on the heat, but since that can take awhile, you may not notice right away. It does adjust the fan speed so it's not blowing cold air until the heat starts to arrive. FWIW, under certain circumstances, it will run the a/c system even in the winter...this isn't to cool the cabin, but to remove moisture so that the windows don't get fogged up. I think, as long as the system is set to AUTO, you'll not have much choice. TUrn that off (I don't remember if that 'sticks' with a power cycle), and you may inhibit it.
The GT is filled with premium components...when people say they want the cabin 72- the car will try to achieve that without your intervention.
FWIW, I hadn't read a specific number for the GT, but on my i3, the engineers have stated that turning off the a/c and opening the windows is only more efficient if you're below 25mph. GO faster, and the drag caused by having the windows open takes more energy (in the case of the i3, that's battery charge) than running the a/c. Unless the vents are set to recirculate, it's much more efficient to get outside air through the vents verses an open window. Old perceptions are hard to overcome.