Who decides what is authentic Italian food?

When you look at Carbonara, everyone will say:

• Guanciale
• Pecorino (or, Parmigiano Reggiano)
• Eggs
• Black peppercorn (cooked in pan and then crushed)
• Spaghetti

But, the original Carbonara recipe called for the following:

• 1 lb. spaghetti
• 6 oz. pancetta
• 4 oz. gruyere cheese
• 2 eggs
• 1 clove of garlic Salt Pepper

This can be found on La Cucina Italiana for the 1954 recipe: https://www.lacucinaitaliana.com/italian-food/how-to-cook/carbonara-how-we-did-it-in-50s

So, my question is this. If I decide to add a tiny bit of butter to my Aglio e Olio, it's apparently no longer that dish. But, you can change up the core ingredients of Carbonara, and yet, it IS the same dish.

If I'm being honest, it's this double think that causes me to question, who truly has the final say on what is and isn't a particular dish?