I see that
# echo $NIX_PATH
shows something similar to @jonringer’s comment:
nixpkgs=/nix/var/nix/profiles/per-user/root/channels/nixos:nixos-config=/etc/nixos/configuration.nix:/nix/var/nix/profiles/per-user/root/channels
It looks just about the same, except for his user-specific prefix. Are duplicate results simply expected? I am thinking that I did something wrong, and that having duplicate results is something that a more advanced user would have if they enable multiple channels, which as a new user was not trying to do.