Just bought a lightly used 2013 Edge SEL and I'm having the same problem. There is an S on the shift pattern with the +/- buttons on the side of the shifter but it automatically goes into manual mode without touching the shift buttons.
The Ford dealer is telling me that Sport Mode was an option because the manual says (if equipped) by the description. It was my understanding that it was standard on all 2013 and newer vehicles. All the other vehicles I test drove had it so I did not even think to check because I saw the S on the shift pattern.