I set $PATH in ~/.zshenv. If you don't, you can't use any of your "extra stuff" in your zsh-scripts, as they do not use login or interactive sessions. And then I unset GLOBAL_RCS so the system configfiles don't override my settings.

In your guide, under ~/.zshenv, you mention that "macOS overrides this for PATH settings for interactive shells", without mentioning why or how. What's happening is that macOS sets your path in /etc/zprofile.

It seems your guide is missing a few global configfiles :) This is the order for an interactive login shell [1]:

  /etc/zshenv
  ${ZDOTDIR:-$HOME}/.zshenv
  /etc/zprofile                 (login)
  ${ZDOTDIR:-$HOME}/.zprofile   (login)
  /etc/zshrc                    (interactive)
  ${ZDOTDIR:-$HOME}/.zshrc      (interactive)
  /etc/zlogin                   (login)
  ${ZDOTDIR:-$HOME}/.zlogin     (login)
  /etc/zlogout                  (login - loaded on logout)
  ${ZDOTDIR:-$HOME}/.zlogout    (login - loaded on logout)

In fact, the configfiles you mention are only loaded the way you've mentioned them, if the option GLOBAL_RCS is unset. And if GLOBAL_RCS is unset, macOS does not override your PATH, because/etc/zprofile is not loaded :)

1: <https://zsh.sourceforge.io/Doc/Release/Files.html>