Glad you enjoyed those clips, nsp. They’re pretty great, as you say. That kind of vocal prowess is rare and your observations are right on. Another aspect of Ella’s scatting that separates her from most other sigers who try to scat is that, while some singers can handle fast tempos (sort of), Ella actually makes the (harmonic) changes! Most singers fake it and simply stay (mostly) in the key of the song, but Ella actually vocalized phrases that clearly outlined the changing harmonies of the tune; the way a good horn player would. Almost unheard of from most singers. Not many could keep up with this:
https://m.youtube.com/watch?v=mo1RS707yxo
https://m.youtube.com/watch?v=mo1RS707yxo