That just simply isn't true, Ricca, accardo, campagna, etc were Cosa Nostra just like any of the American Mafia bosses, and there were/are most certainly traditional Cosa Nostra making ceremonies. Without them, the Outfit wouldn't be considered/labeled La Cosa Nostra by the feds. They would cease to call it Mafia.

I don't doubt that there may have been certain crews throughout history that said "fuck it, you're in, whatever, here are your new responsibilities" but those were few & far between.