Earlier quoted context omitted.
Most of these apps (Facetime, iMessage, Safari, Maps, Wallet, Photos) aren't built using their public SDK but rather have deep dependencies on the OS itself.
Which is why when these apps suffer a security vulnerability they've resulted in privilege escalation (inc. root) previously. I actually think it is a bad look for Apple not to dogfood their own public APIs. Microsoft used to do the same thing with Windows and Office, and it was a bad look then too. Credit to Google on this, since many of their apps are just normal apps. No special privileges or bypasses. Even their…
And Internet Explorer, which was one of the pillars of United States v. Microsoft Corp.