Hi, new-ish member and welcome to Websleuths !
In this particular case I think it's more like an accumulation of actions by the adoptive parents, and not just the moving away.
LE have already said they don't think the boys left by the backyard gate--- yet we have the dad, TW, saying the gate was left open and the boys left while outside playing with the chalk and he was gathering wood.
I do believe LE have some evidence to support their statements.
To say that they feel foul play happened -- some pretty strong wording at this early in the investigation.
We don't know as much as LE do, but I'm trusting where they're leading.
In most cases you see parents who are frantic even if they're not tearful.
The calm demeanor of TW and JW is worrisome; imo.
So sorry about your daughter !