My guess is that what will actually be provided is a generic set of APIs that anyone can plug into to "replace/augment" Siri functionality. This solves a few different problems for Apple
- it prevents the inevitable lawsuits from the EU lunatics about market monopoly
- it allows anyone who feels that Siri is not good enough (and who doesn't care about the likely side effects of a Siri replacement, whether those are privacy, increased power usage or increased cellular usage) to replace Siri. This matches how something like Apple Maps played out, with Apple able to say that the greate advantage of iOS was you could choose best of class, however you chose to define that.
- this avoids them having to bet on any particular AI alternative (Gemini vs OpenAI vs Claude vs Grok vs ...) and then look bad if something happens (that model falls behind? there is some sort of stupid scandal involving the company? whatever)