Just playing the devil advocate: what happens when the answers from a not-Apple LLM are garbage? Who the users are going to blame, Apple or OpenAI, Anthropic, etc..?
I'm not 100% on Apple side on this, I would love to chose whatever I want, even local models, but I get why trey trying to control 100% of the user experience. If they could trust any provider with customers data, they would let them in, since they're not competitors. They would even let Apple not spend a ton of money on developing LLMs....