Which doesn't mean it happened here, it means it has happened elsewhere. You are suggesting that someone walked past the Oldfield's dark quiet and shuttered apartment to knock on the McCann's door. Why not try the Oldfield's?
1) The McCann front door was in near absolute blackness
... and furthermore deeply recessed. Out of sight.
It was at the end of a curved walled footpath that finished there. No passers-by.
If they happened to glance right as they joined the walled pathway, this curve blocked visibility to both Madeleines window and very much so to the front door of 5A ... for anyone leaving the hallway to the other flats
It was beyond the peripheral vision of anyone passing across the car park to the place in the middle of the building where the walled footpath started. Everyone going to and from their apartments had to use this walled footpath ... so they all took the same route across the car park.
Both Madeleines window and the front door were beyond their peripheral vision and both were dark, most especially the front door
2) On the other hand, the front door to the Oldfield apartment was in a very brightly lit entrance hallway. This hallway was not enclosed as it would have been in the UK, but fully open from the outside, so visible to the world. This hallway serviced the stairways to upstairs, with all the flats at different levels and also the entrances to a number of ground floor flats.
People coming and going via this hallway + its visibility to the world outside made the Oldfield flat very less attractive to a potential person set on breaking in/ letting themselves in with a key via the front door to 5A.