Nix bundle on darwin

I’m trying to create a simple nix bundle on my m1 mac by running nix bundle nixpkgs#hello. It says that aarch64-darwin is not a supported system.
Looking at GitHub - NixOS/bundlers I see that aarch64-darwin is listed as a supported system, so I try nix bundle --bundler github:NixOS/bundlers nixpkgs#hello. Yet again, I get an unsupported system error. It looks like the command is using an old version of the flake:

  description = "The purely functional package manager";

  inputs.nixpkgs.url = "nixpkgs/nixos-20.03-small";

  outputs = { self, nixpkgs }: let
    systems = [ "x86_64-linux" "i686-linux" "aarch64-linux" ];
    forAllSystems = f: nixpkgs.lib.genAttrs systems (system: f system);
  in {
    bundlers = {
      nix-bundle = { program, system }: let
        nixpkgs' = nixpkgs.legacyPackages.${system};
        nix-bundle = import self { nixpkgs = nixpkgs'; };
        script = nixpkgs'.writeScript "startup" ''
          .${nix-bundle.nix-user-chroot}/bin/nix-user-chroot -n ./nix -- ${program} "$@"
      in nix-bundle.makebootstrap {
        targets = [ script ];
        startup = ".${builtins.unsafeDiscardStringContext script} '\"$@\"'";

    defaultBundler = self.bundlers.nix-bundle;

Why is it not loading the most recent version of the flake from the Github repo?

Thanks for pointing that out, I just tried using a VM and setting --system aarch64-linux and now I get a different errors instead, but it’s progress!