I disagree. To Vito, the Dons' meeting was confirmation that it was Barzini all along, not a revelation.

Also, per the novel, Luca's tet a tet with the Tattaglia's took place over several months and not in a singular event as portrayed in the movie.

"Generosity. That was my first mistake."
"Experience must be our only guide; reason may mislead us."
"Instagram is Twitter for people who can't read."