Failed to apply custom GTK icon theme, color theme, and cursor theme outside Demo mode

[mbekkomo]

Hello, I'm using regreet as greeter when booting NixOS. I have the following config to customize regreet.

  programs.regreet = {
    enable = true;
    theme = {
      name = "Lounge-night-compact";
      package = pkgs.lounge-gtk-theme;
    };
    cursorTheme = {
      name = "catppuccin-mocha-yellow-cursors";
      package = pkgs.catppuccin-cursors.mochaYellow;
    };
    iconTheme = {
      name = "Lounge-aux";
      package = pkgs.buildEnv {
        name = "regreet-icons";
        paths = with pkgs; [
          adwaita-icon-theme
          lounge-gtk-theme
        ];
      };
    };
    settings = {
      background = {
        path = ../resources/regreet-wallpaper.png;
        fit = "Contain";
      };
    };
  };

The following works in Demo mode. But when I tried it when logging in, it doesn't work at all.

[max-ishere]

A couple of questions:

1. Does regreet start fine with greetd, just isn't themed?
2. Is the demo mode run by the user who has their GTK already themed?