> I’ve lived in Australia and France and I’ve always attributed the taller size of Australians to the excellent state of their ventilation in buildings. Vents (and rooms themselves) are systematically bigger than in France

The average male height in France is 178.60 cm, while in Australia it is 178.77 cm:

* https://worldpopulationreview.com/country-rankings/average-h...

Some sources even have France being higher than Australia:

* https://ourworldindata.org/human-height