Dana A. writes in with this observation about “authentic” focaccia:
I’d be wary of anyone who claimed that it’s potatoes that make a truly authentic focaccia. Don’t potatoes come originally from the new world? And if they do, how is it possible that Etruscans ate them (unless they had space ships/time machines)?
Though I wouldn’t want to necessarily rule out that last point, you make an excellent case. Why didn’t I think of that?