IMO they would not have spoken at the press conference today the way they did and cancelled all searches for tomorrow if they weren't 99.9% sure this was HG.
Except that now they have a crime scene to process, which takes resources away from leading the search, regardless of whose remains they've found.
It will probably turn out to be Hannah; I'm just not convinced yet. I hope in processing the crime scene, they find others. And I hope they look far enough from where the remains were found to do so. They could have traveled a significant distance down that creek bed, from some unknown location, with the heavy rains we had earlier this week.