I don’t think they’d “clear these things up” in a press conference. The police themselves seem satisfied that they know NG made it home, so the only reason for showing some kind of proof publicly would be to attempt to debunk online theories that are upsetting to an already-stressed family or an unhelpful distraction from LE’s investigative work, but even if they did show that, as you quite rightly say, those who have already made up their mind aren’t going to “move on”, they’d just move the goalposts and find a way to make the facts fit their theories.
They’ve got a much more important job to do than to constantly provide evidence that could potentially damage a future case, just to satisfy the whims of some people online. It’d be a never-ending, time-wasting, cat-and-mouse game if law enforcement had to publicly refute every speculative theory in every crime, and nothing would ever get solved.
JMO