In other words, it’s not propaganda. Since the researchers specifically called for prioritizing ventilation improvements in smaller / worse ventilated units, it seems like an odd line of criticism: they’re not saying it can never be safe for anyone ever but that in practice it isn’t safe for tens of millions of people.
It was done on people suffering from asthma - with all the reason in the world to improve air quality. Replacing gas stoves with electric stoves a huge effect, on the other hand "installation of a ventilation hood over an existing gas stove in 15 other homes did not significantly change NO2 levels".
You're not helping the air quality if all you do is move it around inside.