I also think these cases could possibly be related, however, there is one major difference between them: the girls in Iowa were transported to a different location. There's quite a bit more involved with that.
It certainly doesn't rule anything out, but it does add questions, imo.
The girls from Iowa were found so late, there probably were not enough clues. With Delphi girls, there was a lot of information. So unless there was a direct connection (some item from IN left in Delphi CS, for example), or some specific person lived close to both places, looking for the analogy might muddle the waters. If the Delphi killer is apprehended, his connection to IA case needs to be checked, of course, but as of today, I don’t see any, except for “neighboring states”, and “two tweens in one case, two teenagers bordering on young adults”, in the other.
Trail killers, sadly, exist in every state where people hike and bike. As Jonelle Matthews’ case seems to indicate, any adult can abduct a young girl and kill her.
The only thing that comes to mind, Steve Pankey and Jake Patterson are of a very similar psychological type, maybe the person who killed the Delphi girls is not unlike them. I would look for similar traits. It is interesting what both might say about the case.
(In IA, sadly, it could be any aging pedophile).