The issue is that the leaked emails were stolen and are being released by an actor with the capability of altering them (replacing the word "didn't" with "did" for example, or deleting context). If you cannot eliminate the potential for contaminated data, then you cannot either confirm or deny. So no, it isn't the Dog that Didn't Bark. If the press or HRC or Podesta says "these are real" and then a fake one is found, how do you go back and undo that?
If it is Russia, they will certainly release all real ones until the final week, and then who knows? What if we all accept they are "of course real" and report on them as such and then one appears the last minute (insulting Florida, Ohio, Virginia, Nevada, NC etc) that alters a swing state?