Yes, both the parent and I agree that Oak Park is a suburb (and a lovely one by the way; I hit up Amerikas every time I visit)—I was pointing out that he was making an argument of the same style that he was criticizing (using his own definition of a suburb to advocate for his own definition of a suburb).

In any case, I think there are multiple valid definitions for suburb—one which talks about smaller towns on the periphery of large cities and another which emphasizes postwar design principles/philosophies. I don’t see the point in arguing for a single true definition; language doesn’t work that way.