I have no idea if the identifiers of the photograph had the benefit of viewing both the photos at the same time. Possibly that is the reason they identified them as two different individuals.
The two Swann-Harper photos are unmistakably the same person. One shows a flower with leaf in the lapel and the other shows a Warren G. Harding Presidential Campaign Button (which helps date the photo on the right).
Is the young man Charles Abney or Will Todd? Hopefully, one day someone will be able to help determine his identity. The only thing we know for certain about the photo at this time is when the photo was taken and that the subject was happy on Election Day as his candidate won!
Read more about President Harding here http://www.whitehouse.gov/about/presidents/warrenharding