Some quotes from the article:
Their 1992 conviction...has effectively been overturned by a May 2015 Court of Criminal Appeals ruling 'granting relief' to the Kellers...but the ruling was not accompanied by actual exoneration.
In the absence of an exoneration from the court, there remains one person who can act upon the complete absence of evidence...District Attorney Rosemary Lehmberg.
In previous local exonerations, Lehmberg recalled, DNA evidence eventually led away from the person convicted. In this case, the absence of any physical evidence...has had a perverse result: it has thus far prevented Lehmberg from any further action.
While I'm not sure if it's technically correct that there's no evidence of wrongdoing whatsoever, it seems strange to me that in a legal system where the defendant is innocent until proven guilty, an appeals court would not be legally required to exonerate the convict if unable to find any evidence (or the single piece of evidence was retracted, as in this case) with which they could have rendered a guilty verdict in the first place.
Why is it possible for a convict not to get exonerated even if the only evidence against them gets retracted?