It throws a curveball to the viewer, and it also serves the purpose in that even if Frankie had died, word would have gotten out, maybe by the bartender, that Micahel was the one who killed Frankie. In my opinion the line works one way or another, and I think that FFC felt the same way.
Don Cardi
Isn't that along the lines of what Alfred Hitchcock called a Maguffin?
"Io sono stanco, sono imbigliato, and I wan't everyone here to know, there ain't gonna be no trouble from me..Don Corleone..Cicc' a port!"
