Voice processing is AI and was done by Apple servers. Previously, only the keyword "Hey Siri" was local. Onboard AI chips will allow this to be local. The actual queries will go to the servers. Phones do not have the power to run useful LLM locally- at least not with the near instantaneous response times phone users expect. A 56 Watt 128GB RAM M3 Max does around 8.5 tokens/second.