I agree it could go both ways, what DM said about being confident they wouldn't be found there on his family's (mother's?) 2 acre property.
Also depending on the context of the interviewer's (?) question he was responding to, which if I'm keeping up here, was redacted?
On the face of it at the time he said that, it could be as simple as it seemed on the date he said it, that perhaps he had done his ultimate best as a bereft stepdad having searched high and low in every spot he knew of they could have been hiding in or fallen into or where there was dangerous terrain on those 2 acres.
My property is of similar size and rural in nature.
About half of it I know like the back of my hand, and any signs of new or unusual disturbance would be obvious to me, and the other half I could search without much effort in a few hours time.
So I can relate to him saying that with confidence at the outset and having no doubt they weren't thereabouts after he felt he had thoroughly searched it all.
At the same time, he only had his own eyes to look with, and his own knowledge of the property, for IIRC the last 2 years (?) living there with his newer partner & kids.
As I did when I was super surprised to discover a new neighbor had been encroaching on the "way back" portion of my property while I was busy with other things and couldn't walk it all on a regular basis.
I didn't ever hear anything, see anything, or have any clue the new neighbor had cut trees, put up fencing and gates in the way back part of my property until months later.
When I happened upon it one sunny day when I had time and went beyond the acre around my house that I frequent to do some brush clearing and check on water flow in the swales that usually flowed away off the property and had become stagnant, because of changes the neighbor had made well out of sight that blocked the water flow in the swales to make a wallow pond for their ducks "because we weren't using it and they didn't think I would mind".
So just sayin, 2 acres of natural habitat surrounding my domicile was enough of an expanse for me not to know what was going on throughout it all for awhile.
And if DM's place & his mother & brother's were all on the 2 acres or they each had their own acreage as part of a larger parcel, with neighbors, we don't know I don't think.
But LE does, and are coming back to the area to search again with cadaver dogs, and I both hope and don't hope, contradictorally, they'll find something that they & DM might have missed in their initial searches for Lilly and Jack.
Still holding out hope they were spirited away by a good samaritan and are alive somewhere happier than ever, instead of being found deceased near home after wandering away.
MOO