They explained that their concern is with COVID/shared ventilation and it being way too cold.
If they were concerned with shared ventilation why move there in the first place? Also if it's "too cold" then why are they making the argument that they can just "shut the vent in the room" in order to appease the landlord for having the window open? They could shut the vent and keep the window closed to keep it warmer in the room.
If you want to have sympathy for people struggling with housing and high expenses, what about the rest of the people living there that have to pay money they don't have in order to cool the entire neighborhood? Your empathy shouldn't only apply to whomever tells you their sob story first.