True, I had to learn that the hard way: expecting the arhitect to know ...
So I was told by the agency this is by design, no deployment mistake. No comment on why other apartments in the same building have a different setup.
Then I read the v-Zug manual once more, it seems the carbon filter needs to be washed as well, and re-activated every 2 months ... I guess my bad, a clear case of RTFM, as I have not touched it for 8 months.