Puzo was one of those authors (like Ian Fleming of James Bond fame) who couldn't resist passing along every bit of erudition he'd ever accumulated. Evidently a woman he knew had had that operation, or he knew a doctor who performed the operation, and so he learned about it and got fascinated with it. You've found, as did many of us here, that the sole purpose of all that Lucy-and-Jules crap was so that he could describe her operation. Made me feel used!
Puzo also spent plenty of time in Hollywood before publishing GF. The sole purpose of all that boring Johnny-and-Nino crap was so he could show off what he learned about how Hollywood works. Objectionable as it is, it's nowhere near as bad as that s***load of Hollywood BS that he piled on--and nearly sank--"The Last Don." One of the reasons that the TV series was better than the novel is that the TV series dispensed with most of the Hollywood BS.