Stay Put with more than 2 flats per floor

I understand that a purpose built block does not need lobbied corridors if there are only 2 flats on each floor, close to the stairway.

I have come across a block that has 4 flats on the ground floor (the most distant one is about 7-8 metres from the entrance door). There are 2 flats on the first floor and 3 flats on the second (top) floor. There is AOV at the top of the stairway.

The building operates a Stay Put procedure. Is this acceptable? Can the  ground floor and top floor have more than 2 flats without being lobbied?

Thanks