@Marie82 @Sean433
Thanks for your replies. I have lived in Europe much of my life, and lived almost 20 years in Italy, in both city centers and in country houses. The Italian concept of living space is not so different from the American concept, and value their "metri quadrati" perhaps more than Americans. Apartments in city centers were typically quite large until recent years, when many were chopped up to be rental units. Italians also prefer larger bathrooms, and will never compromise on the space required for a bidet. Italians do make fun of American-style McMansions, but that's changing too, and you will find plenty of them in the outskirts of places like Brescia, Varese, etc.
But all this is beside the point. Hosts really should provide information on the apartment's total living area. Sure I would like to see a floor plan too, but would be happy with a total area calculation. As I wrote above, it is one of the few objective facts that can be presented for a property.
Certainly AirBnb lodgings are a good deal compared to hotel rooms, and perhaps hosts should charge more. That is another discussion for another day. As for the original topic of transparency, I now understand that I should never stay in a place whose photos were taken with a wide-angle lens, even if that considerably limits the options in particular locations. Thanks for all the replies!