The book assumes running Darwin/OS X, which has consequences specific to that, eg https://github.com/below/HelloSilicon#listing-9-1 but one of the biggest changes is the GPU attached to the arm core, resulting in non-native Apple-specific code. It may not affect the ARM CPU core directly, but if someone is running on Apple Silicon you can assume MPS support whereas you cannot do that for ARM64 targets.

It might also be worth reiterating that this book is, itself, a port from the original, more generic ARM version.