That's exactly why the Corleones couldn't have been one of the five families.

This is a work of fiction set against a somewhat loose historical interpretation of some events and figures.

Fontane was supposed to be Sinatra
Moe Green was supposed to be Siegal

But Don Corleone was not supposed to rersemble anybody. He was the head of a fictional 6th family, whose story was told against the historical framework of NYC oranized crime and the five NYC families in the early 1940s, and, as such, he was none of those family heads.

It was not that Puzo was hesitant to have Don C. compared to one of the NYC Dons. It was that he couldn't be compared to any of them.

Haven't you yourself have posted the opinion that Don C. was an amalgam of features and traits of the various NY Dons at the time?