I've taken a short poll of a few friends who are in rental properties. Not one of them airs their house regularly. Two of them were surprised at the idea that they'd have to. They've owned or lived in newer houses almost exclusively, and the idea that they'd have to open windows regularly during the winter time had never occurred to them.
Which I'm glad of, because it had never occurred to me. I took the poll (of English people) because I'm not from this country, have always lived in newish build homes, and this has never been an issue.
So yes, if you expect people to have to open windows throughout the winter, you need to tell them. Don't just bury it in their letting agreement either, because we all know how closely people read those (some do, some don't). Get the extractors put in, get the dehumidifier and tell them they need to use it regularly, because it is in an issue in that house.
I currently rent, have rented a couple of properties in this country (have now purchased a house, thankfully) and have had any number of experiences with poor ventilation and ancient, inefficient boilers. I lived in a Victorian terrace where we'd have to ventilate daily, then heat the place back up again at our expense with the old-fashioned boiler provided. It wasn't nice, and we moved on quickly.
There are two sides to every story, I wouldn't tell you you are being U, but that yes if you expect people to do something in particular, you need to be very clear about that when they move in.