That is exactly the point they made in the NPR story. The woman who was featured in the story, learned about her condition because they were doing some kind of blood tests on her and her family (I don’t recall the exact reason) and the doctors told her that there was no way that two of her sons were hers because the DNA didn’t match. But they also extended the scenario to someone leaving one set of DNA at a scene of a crime (blood, for example) and getting away because the DNA in, say, a throat swab was the other set. Yeah, the whole situation is, as they said, “mind-bending”.