I always assumed Puzo included it because it represented reality in Hollywood.
On TCM they have interviews with old hollywood people. One night they interviewed an executive assistant who worked at one of the big studios in the 1940’s. He said Elizabeth Taylor and her mother came to sit at their table to meet the head honchos. She was 11 or 12 years old dressed provocatively with a little snake drapped around her neck . He said the snake kept dipping his head down her chest into her blouse and every hollywood guy at the table wanted to be that snake.
It was amazing that the old guy had no trouble telling this story nor did he seem to feel any shame over it.