I've driven both 2010/2011 and currently own a 2012 GT.
Sometime either late 2011 build or for MY 2012 onwards there was a change on how the hatch buttons work.
PRE 2012 - Center button and button inside car and 3rd button on the remote open the small trunk lid. Side button (to the right) opens the large lid, same as 4th button in the remote.
MY2012 and on - Exact opposite as before... Center button/Button inside car/3rd button on remote open the large hatch. Side button in trunk lid/4th button in remote opens the small lid.
Btw these functions can be changed by coding. (I changed the 2011 I had for a while to work like this).