It’s easy to understand why someone might think folding pizza started in New York City. Most of Italy eats pizza with fork and knife, so it appears as though the tradition started after the dish left its native country. But we have to keep in mind that pizza is not necessarily Italian to begin with, it’s Neapolitan, and the culture of Naples is key to the understanding of pizza at its origin. Naples was an active port and one of the most densely populated cities in Europe at the time pizza was gaining popularity in the 19th century, but as a peasant food it was not often eaten by outsiders. Even today, the most common reason for visiting Naples is as a connecting point to go somewhere else (Capri, Amalfi, etc). Pizza was a street food enjoyed by the lazzaroni (peasants) thanks to its low price point. It’s unlikely these people were eating a meal at a table with fork and knife. But because of their circumstances and the culture of Naples, this method was isolated until its resurgence a century later in New York City.
To sum it all up, people were definitely folding slices of pizza before post WWII NYC, but it was only happening in Naples and never achieved the status of compulsory eating method the way it did in New York City. So your 20-something friend might want to be careful about using television programs as historical references.