Well, that’s why Apple forbids use of private APIs in the App Store apps. If you built all your tech stack on the foundation of some peculiar nondocumented platform’s behavior, don’t be surprised when this stack breaks.
This is not an API. It's the handling of writes to memory the process has protected. In the past this would generate a signal the process could handle and recover from. Now it generates a sigkill which is uncatchable / unrecoverable from.
These behaviours have been historically well documented.
And, why not? macOS is Apple’s IP and they have all rights to do with it as they want. Buy the way, Chrome/Node.js JavaScript engine uses JIT compilation too. Are they affected?
It is not obvious to me that this breaks POSIX compatibility. The kernel may choose to signal a process with SIGSEGV on a memory protection violation but I can't find anything that suggests this is required.
Last I checked, macOS formally maintains POSIX certification. Linux is not POSIX compliant, so I wouldn't use Linux as the measure of what is correct behavior under POSIX.
These behaviours have been historically well documented.