Well I'll be damned. I might have to switch phones after all even if all the new ones are oversized.
Unfortunate this looks opt-in for third-party apps. I wonder how much adoption there will be. Hopefully WhatsApp and Signal will adopt it right away?

Blog - Memory Integrity Enforcement: A complete vision for memory safety in Apple devices - Apple Security Research
Memory Integrity Enforcement (MIE) is the culmination of an unprecedented design and engineering effort spanning half a decade that combines the unique strengths of Apple silicon hardware with our advanced operating system security to provide industry-first, always-on memory safety protection across our devices — without compromising our best-in-class device performance. We believe Memory Integrity Enforcement represents the most significant upgrade to memory safety in the history of consumer operating systems.
Blog - Memory Integrity Enforcement: A complete vision for memory safety in Apple devices - Apple Security Research (security.apple.com)