He might be saying that someone else was there, using the rental space, that night? LE might have to check on anything he has said in his defense to make sure he's the perp and not just the owner of a house where something happened?
Getting rid of the bed base and mattress sounds suspicious, but what if he had someone in the airbnb and thought afterwards that the bed had a strange smell to it and he'd better get rid of it?
Also, even if LE found things in the property that were forensically suggestive, they have to get enough evidence together to tie that evidence to both ML and AA.