You know, we heard it about Delphi too. "But someone would have seen a total stranger in a town this small, it must have been someone they knew or felt safe with". And yet, not a single person saw squat, these poor children were grabbed in broad daylight, killed (savagely it sounds like) on someone's property, and the perpetrator seems to have vaporized with no clue as to who it was.
Also, why would the local police be kept in the dark, if that's true? If Mollie is the focus, the investigation into her disappearance needs everyone, certainly the local resources, who would still have jurisdiction over their own turf.
We see this in military issues as well. A retired general comes on cable news and characterizes what happened somewhere on a mountain in Afghanistan in a US military operation. If the media can't find any facts, it looks for someone's opinion.
I can buy that someone she crossed paths with previously who perhaps had singled her out might be responsible, but let's not forget that Karina Vetrano and Vanessa Marcotte were both jogging and were ambushed in daylight and swiftly killed by total strangers who were opportunistic predators, and no one saw it.