The extensions present in the M1 are not used at all by Apple’s public compilers. From the perspective of a 3rd-party macOS developer that doesn’t reverse engin

The extensions present in the M1 are not used at all by Apple’s public compilers. From the perspective of a 3rd-party macOS developer that doesn’t reverse engineer, it’s just a regular arm64 machine. This allows Apple to deprecate/change those extensions over time without developer involvement, and even use Cortex reference designs where it would make sense for them.