The Vinaya story mentioned by Nattier in Cullavagga is understood by Levman as follows:
The Buddha wanted his very words, in his own vocabulary and designations, memorized, repeated and recited. This is the gist of the Cullavagga incident, and the significance of the phrase sakaya niruttiya. (Levman, Bryan Geoffrey (2008-2009): Sakaya niruttiya revisited. In: Bulletin D’Etudes Indiennes 26-27, S. 33–51).