I made a post about this a while back. I also realized the difference but it was after I bought the car, and it isn't a significant factor to me. I have a 2017 gt350 base line, not one single option added, because trim packages are worthless to me. If it doesn't make the car perform better, I don't want it. So it that regard, I also noticed that the Launch Control button was available on the dash, but other people had a exhaust button there. It would appear to me that it is a symptom of getting the upgraded deck/radio/premium, whatever that package is.
I think the better question is, why the hell they put Launch Control down there instead of Exhaust Mode. I will never use that Launch Control, and the GT350 is not a drag car, so it begs the question why the hell they thought it was a good idea? I am currently trying to discover if there is a way to re-map the functionality of the button from Launch Control to Exhaust Mode, so I don't have to navigate menus every time I turn on my car to flip open the exhaust. I like to be a good neighbor and use the quiet mode late at night or early morning, and a button for Exhaust Mode is much more practical in that location than stupid LC.