It’s possible that police sharing some details with the media was to stir up their target, and the fresh information wasn't as significant as imagined. Police intentionally putting snippets out there with the aim of generating conversation to be captured on surveillance devices, in the hope it would lead to significant evidence.
There’s been a highly planned strategy in play beginning with David Laidlaw appearing on the Sky episode, followed by the leak about a new POI, then police returning to Benaroon Drive and releasing photos and video on the anniversary. Then the pressure increased to a new intensity with the big search, NSW CC, AVO, assault charges laid etc.
All the while the fosters would’ve been under heavy surveillance, a huge investagative tactic that police were hoping would pay off. Whether it did or not time will tell, it doesn’t seem that they got the concrete evidence needed to lay charges over William’s disappearance. All IMO.