For the cores working hardest to achieve the absolute lowest cpi running user code, this is true. But these days the computers have computers in them to manage the system. And these kinds of statements aren’t necessarily true for these “inner cores” that aren’t user accessible.

“ RTKit: Apple's proprietary real-time operating system. Most of the accelerators (AGX, ANE, AOP, DCP, AVE, PMP) run RTKit on an internal processor. The string "RTKSTACKRTKSTACK" is characteristic of a firmware containing RTKit.”

https://asahilinux.org/docs/project/glossary/#r