Calculation of rainwater infiltration realistically??

Who of you uses an infiltration system?
I have now had the infiltration calculated for our new building based on the soil survey and the roof area. Even though the internet research and my own recalculations showed that the calculation is actually correct, the whole thing seems somewhat excessively large from a logical common-sense perspective.

The conditions are:
190 sqm roof area (42° and flat roof - runoff coefficient 1)
Soil: medium sand (kf=0.0001)

Allegedly, the trench infiltration should hold 4000 liters. Isn't that a bit excessive?
I had the whole thing calculated with Graf EcoBloc elements.

I don't want anyone to recalculate it for me here, as I have already done that myself, rather I am looking for a comparison of what you have installed and whether it really adds up and makes sense to dimension the infiltration system that large.

When I read that during storms/heavy rain it can easily pour 50l-60l per day or up to 25l/h, I don't find 4000l for 190m² to be oversized. You probably don't want water in your apartment or basement either.