Possible Reasons for keeping DNA quiet:
1) They may have connected his DNA to other unsolved cases, either in Indiana or other states. Possible SK. "Don't terrify the public ".
2) The DNA may be such that some characteristics of the DNA may be carried by only a tiny percentage of people (i.e. a gene for albinoism or whatever), that substantially narrows a suspect pool. A suspect or suspect's family may be aware he carries a rare gene. If the family is not aware, why tip them off as LE builds a slam-dunk case? If they are aware, then DEFINITELY don't tip the suspect and/or his family off.
It is also now possible to narrow down DNA from identical twins, by examining more ( a longer length) of a strand of DNA from both twins.
3) They have narrowed the DNA down to a specific (large) family and are slowly eliminating the males as possible suspects.