Thank you for this! I have exactly the same problem and was waiting for the solution to present itself, which it now has.

Aside: I use NixOS with home-manager (on linux and mac), which makes this trivial [1]. Added the following lines to my home-manager config:

  programs.git = {
    enable = true;
    ...
    includes = [
      {
        condition = "hasconfig:remote.*.url:git@github.com:<work>/**";
        contents = {
          user.email = "<work email>";
        };
      }
    ];
  }

That certainly looks less trivial than writing it directly in your .gitconfig file. It's the same condition and setting as what's in the article, but now with a build/templating stage and a new programming language to learn with unusual syntax.