And the signatures leads to another discussion. If the Delphi killer purposely left signatures, what satisfaction would he achieve if the bodies were not found? The killer in Evansdale appears to gone to great lengths to ensure the bodies would be hard to find, if not impossible. Such an effort might cause such signatures to be eliminated by weather and animals. A wasted effort in the mind of the killer if he left a signature or signatures. That seems to make the argument that the two crimes are not directly related. Unless, again, a killer evolved.
Snipped to focus on the discussion of signatures....
I think you are equating a signature with a "calling card" of the killer that he leaves behind for others to react to. I think that a signature, if Robert Ives is using this term the way psychologists do, must be thought of first and foremost as an outward expression of the killer's inner fantasy about the crime. It's always done for the killer's emotional need firstly. Maybe in some cases it's also done to shock others if that's part of the fantasy but it need not always be.