JMO.
Once again, in the linked article, LE says absolutely nothing about the DNA that has any meaning.
"Investigators say they discovered DNA evidence at the crime scene where two Indiana teenagers were found murdered last week. That evidence now has top priority for processing by investigators."
This is basically the same thing LE said in another article about needing to process the DNA they found at the crime scene. It could be the girls' DNA or it could be contamination DNA. LE is being very careful to not say they have the perp's DNA.
"DNA evidence" is a large tent that can encompass a lot of testing and results.
Even if there was a hair left at the crime scene by the perp, the hair root and bulb would need to be present to extract enough DNA for identification.
In addition, the crime scene was not in a secure climate-controlled environment. The evidence and bodies were outside in the cold February weather, with a blanket of wet dew near a creek. DNA collection from that type of compromised crime scene would be difficult under the best of circumstances.
How long does it take to process a good sample of DNA? It doesn't take two years. By now, the sample should have been at Parabon NanoLabs or some other lab for processing, extraction and familial/autosomal DNA tree-building.
LE says they're back to the beginning. They've changed what the suspect looks like. They're begging for tips on a vehicle seen one afternoon over two years ago. If LE had the perp's DNA, they could already have a better sketch of what the perp looks like from Parabon and an idea of who the perp's family is by now.
They could be building the case on actual evidence. I don't understand why LE said just months after the murders that familial DNA testing and genealogy was "on the table." It either is, and should have already been used, or they don't have what they need to go forward with the testing.