That article is very annoying as it is anchoring into silly technicalities. Yes, modern pizza came from Napoli and Italy (as a unified country) didn't even exist back then. But it is a complete sillyness not saying modern pizza is not Italian.

"Let me repeat that: Pizza isn’t Italian.

Pizza is Neapolitan. It’s a distinct speciality of Naples, developed at at time when Italy didn’t even exist as a nation. Saying pizza is Italian is like saying haggis is British. It might be technically true, but not really. "