Strict ventilation in a flat duct in the floor structure of the upper floor?

According to DIN, stacks from 5m are also ventilated, and a cellar underneath doesn’t help either

When I asked about the cellar, I was referring to the fall height in the vertical. This must not exceed 1 m in single or collective connection pipes. Since we are talking about a single connection pipe here and a base pipe connection is already ventilated through the roof, I would like to point out again that the additional stack can be omitted.

From which regulation do you derive the 5 m?