Close door ventilation grille?

As a landlord, I would prohibit locking it because I do not know if someone is drying laundry inside or leaving a steam bath while showering. As a tenant, the dismantling would deter me if required.

(...) I would foam the openings in coordination with the landlord and cover them with a foil (if a reasonably matching one can be found).

Why should a landlord agree to such botched work that is more than clearly visible? That way, the doors will be ruined for good...

Why should a landlord agree to such a botch job that is obvious to see?
That would permanently ruin the doors...

Why?
Because you can simply cut out the foam including the covering afterwards. The covering is only on the hole, so it's basically like a rectangular plug.
After moving out and reinstalling the old ventilation grilles, you won't see any of the "botch" anymore.

Then you can also put styrofoam in. It's easier. Because when a layperson works with foam for the first time in their life, it's usually a mess and at least the first door is then completely ruined... especially if it's a CPL door.

The ventilation grilles were probably necessary at some point because gas heaters were installed in the rooms (no longer today). Of course, cold air from the daylight bathroom, as well as noises and odors, are bothersome.

Perhaps one should also question whether they might be necessary due to a newly installed ventilation system or the required heating in the bathroom (how is the bathroom heated?).
Because if you talk about cold air, one might have to become alert.
But I also do not have the necessary knowledge – in the house construction forum, for example, ventilation systems in a new building are discussed, where doors must allow airflow for physical reasons.
So if the apartment or the building was renovated, might they still have their justification?