I could not agree with that more! Too many times, "authentic" really is "what I grew up with," and that doesn't really mean anything.
I watched a program a while back, and on the subject of authenticity (in a larger discussion about pizza), the host made the argument that a pizza from a particular region used the ingredients that were local - this kind of tomato and that kind of cheese, etc, and then that somehow, in order for a pizza made a million miles away in, say, Japan, to be considered "authentic" would have to use ingredients that just weren't available, and that in his mind, "authentic" meant, "do what those local cooks did - use readily-available local ingredients." So, if you're in Japan, and you don't have tomatoes grown at the foot of Mt. Vesuvius, then use the locally-grown tomatoes you do have, and now...it's "authentic."
I liked that perspective.