This is definitely true, the key thing here is that they don't have to (and assistant does work outside of service). In addition, there's no guarantee that "tha

This is definitely true, the key thing here is that they don't have to (and assistant does work outside of service). In addition, there's no guarantee that "that was not for you" will actually delete details about the last command, but Apple doesn't even attempt this. You have no idea if something Siri shouldn't have heard will end up in a training dataset (disclaimer: I'm saying this in ignorance of the Siri privacy policy).