Sounds like they bypassed the need for that altogether.
While I get the whole 'sideloading is a security threat' arguement, it really doesn't hold up to scrutiny when you can send malware to any phone via invisible SMS parsing bugs. Apple might have a leg to stand on if their history of threat mitigation wasn't so rocky[0] in the first place. The simple fact of the matter is that they're fighting an infinite war of attrition that's not in their favor. State actors and even private interests are now overwhelmingly capable of buying and implementing zero-day exploits, so a more logical security effort would aim to strengthen the kernel and, you know, actually mitigate these threats. Enforcing type-safety and memory safety at a lower level would be a good start, but Apple knows that isn't very marketable (and they have enough zombie XNU code in MacOS and iOS to constitute an new operating system altogether).
By this point, most people call me a security nihilist, paranoid schizophrenic, or an architecture astronaut. Maybe so, but modern threat models are built around pragmatism, not idealism. Apple can wave as many flags as they want, but seldom does that actually effect the overall security of iPhones. NSO will just reach into their catalog of stockpiled vulnerabilities and spin up a new build overnight. If Apple doesn't recognize this before it's too late, I reckon their OSes will become the modern Windows: confusing abstractions of well-understood concepts, with a dead-set focus on how the user perceives the OS, not how it actually functions.
[0] https://citizenlab.ca/2021/08/bahrain-hacks-activists-with-n...