Looking at the floor plans, and Trulia and Zillow, the front of the house is placed and looks, as if it's a back entrance, to me, but it's not. The door does have a keypad and appears to have a deadbolt too.
Where the stairs come up from the first floor is facing the front of the house which would be facing the parking area. I think. Based on the reports of the victims being on the 2nd and third floors, both slider doors would be of pretty easy access on those levels. For exit or entry. The overhead is just to show the terrain and how easily someone could stalk their victim.