So if this floor plan is accurate for their home, there's a door to the side out of the garage (trying to read backwards on the flipped image!) that she could have theoretically left through to go to the rear of the house? I think that was what CW was implying could have happened in his fantasy version of events he gave the cameras.
ETA: I think he was really going to try to push the kidnapping angle, having found himself with less time to stage her and the kids' 'voluntary departure', get rid of her car, etc.
When asked in his porch interview: "How would she have left the house if she did leave the house?"
CW goes straight to: "I don't want to put anything out there like... suspecting, like if somebody pulled in there in the back and because we have driveway back there from the new town homes but... It's so hard to tell, like. There's no cameras in the back yard or anything like that, so... It's really hard to even suspect anything right now as far as how she could have left. Or if somebody came and picked her up... or somebody took her."