No, I think that is a good observation. One way to decide is to look at documents that occur around the same time (the pattern of recording for the time period) and see is the name is usually last, first or first, last.
In this case, you are quite right...the pattern is last - first (for the groom and the bride). So the groom is Aniello Graziano..
I'm sorry if I confused you
Certainly Graziano is most widespread today as a surname than Aniello.