A dog's understanding of fairness

There an interesting article on Wired.com about a recent study that claims to show dogs have an understanding of fairness. Basically, two dogs are asked to dog a trick ("give me your paw") but when only one gets a reward, the unrewarded dog stops doing the trick.

I thought it was a pretty good demonstration that dogs do have more complex emotions than a lot of people give them credit for, but one psychologist had this complaint about the study:

One such nonplussed scientist, Clive Wynne, a psychologist at the University of Florida, told the AP that he wasn't sure the experiment measured fairness at all.

"What it means is individuals are responding negatively to being treated less well," Wynne said.

To that I say, "Well, duh!" Isn't that basically what fairness is all about? Being "treated less well" is in fact the same as being treated unfairly. That's like me saying, "The study doesn't measure fairness at all. It only shows the dogs are responding differently when they are treated unfairly." Wouldn't that statement just be completely contradictory?