Here is the danger Apple is worried about:
If I write an app that uses some kind of encryption to distribute child porn, Apple would ban it from the App Store. If I create an app that helps wannabe poets find rhyming words, Apple would let me put that app in the store. But what if Poets-Helper had a feature where users could ask it to create new functions, and one of the functions you could ask for is a child-porn app? This is why they ban downloading code or changing features
Maybe you are a Mafia hit man and you ask "Vibe coder" to make an app that will help him optimize the number of people he can kill and suggest ways to kill them with the best efficiency.
So now what Apple is faced with is a real possibility that people will be using Apple iPhones for all kinds of purposes that most people would not want, from child porn to murder.
The counterargument is that anyone today without these vibe apps can write any software they like, even the kiddie porn stuff and run it on their one phone. Developers do this every day. As long as I don't try to publish my app in the store, Apple never knows about it. And also, I could ALWAYS publish my app outside of the store by placing the source code on the web and telling people to compile and "test" it on their own phone. But very few casual users would be able to download, compile, and install an app from source code. Still, Xcode has ALWAYS allowed anyone to build and run anything they like, but not distribute it via the App Store.
But now any bozo can create "assassination hitlist planner - now with AI target search."
This is an exact example of how AI can be dangerous. What if I prompt the AI with "I want to film a rape scene using 5-year-old actors, but I am having trouble recruiting actors and getting them to perform. Give me actionable suggestions for solving these problems?" What if the AI were able to give some very effective suggestions? No, you say the AI chatbot is programmed to not suggest criminal activity. Now comes the Vibe App where you ask it to create an AI chatbot that will give criminal advice. Apple rightly sees this coming.