My theory is based on this article from last summer:
Delphi detectives working closely with investigators who cracked Fort Wayne cold case
“While officers wait for that one last tip, investigators are using other tactics to track this man down, including DNA which is being analyzed by the Indiana State Police crime lab.
“That information is then put into a national database,” said Sgt. Riley.”
To me it would make sense if they got a hit on familial DNA. They wouldn’t have a suspect just yet, just a link to one. And they probably would not want to answer questions that could reveal the identity of the link, as that person would not be a suspect.