Well, Italian *nonnas rarely used more than one pan for cooking, and it was very common to just put pasta without the sauce in the plate, and a generous spoonful of sauce on top. This is what you used to find in restaurants, too.
The cooking water in the large pan is a rather new thing.
Or maybe it's something just from my region :)
Can't speak for all italian regions as there are many differences; but this "spooning some sauce over naked pasta" right on the plate always struck me as positively un-italian. I would always expect the pasta and sauce to be mixed in the kitchen, and the pasta to be completely coated in sauce when the plate reached my table. Maybe it's something italian-american ?
It might be a potato culture thing as it was historically common when pasta showed up on shelves in Sweden that the older generation just went with the instructions separately, cooking pre-peeled potatoes loses so much of it's flavor so if boiled, it's done so separately, getting a new ingredient you probably do it as you've always done.
The cooking water in the large pan is a rather new thing. Or maybe it's something just from my region :)