The way the girls were abducted,killed and the bodies dropped in the woods. IOW they had considered at the time and still do that the same person killed all three girls - I.E. linked.
but does that MO link to the Ramsey killing? the method of death, notes left behind, etc.
Henry Lee Lucas admitted to killing untold number of people. Some it was proven he did indeed kill. Others LE gave him credit just to clear their cases. But many he confessed to killing because of his fantasies and/or to keep himself from being executed as long as possible. I hate to say it but this is looking like it might be taking the same course.