This.
If our smartphones really did send everything all the time to a 3rd party, imagine the data and battery consequences. 
Taken a step further, the sentence is worded badly as well - Siri, AFAIK, doesn’t send anything to nuance, all that data stays in-house at Apple. YMMV about how you feel about that, but of all the choices they’re the ones profiting the least out of your shopping habits (for example), or making revenue from your ad choices, etc.
I also wonder how much longer it will be that way. Surely the whole “send this back” system is in large part because the storage/horsepower for the voice recognition system isn’t quite there yet on one’s phone. I’m sure the mfrs. would much rather be able to advertise those functions for use even without data access when needed, after all
