AI assistant will be a short lived gimmick, in the sense that if you don't mind it being completely inaccurate for all the integrated tasks you  give it, then it will  SORT OF work.  But when it makes mistakes, it will move beyond just annoying (like when alexa doesn't understand your words) to destructive and catastrophic.   Apple doesn't want to use its own AI because it doesn't want that responisibility.  It informs you that you are using OpenAI.  Because its an unreliable toy.