Not really. I'd been watching and enjoying the film for 20+ years before I ever even knew about this revelation in the book that young Santino watched his father kill a man. A well written novel always provides insights and incidents that give depth and background to a character, because a novel has the time to share such things. Using this particular moment in the movie or even referring to it would've done no such thing.

Sonny's 'enthusiasm' in the 'BADA-BING' speech is partly due to his amusement at his civilian, war hero kid brother who presumedly knows NOTHING about the Family Business daring to come up with this outrageous master plan to kill a New York Police Detective.

Apple