To emphasize this point: dleslie's comment is valid on a blog post "we tried Nix for a while to manage our dependencies, we are just building an app and want builds to work, and we decided to move on". For an end user, it is absolutely understandable to assume "nix = nixpkgs".

But as kfajdsl points out: that's not what TFA is. This is a company building a product on top of Nix. Package management is their expertise. Anyone using Nix in that capacity understands the distinction between nix and nixpkgs. Which they certainly do--GP only remarked it was odd they didn't explain it, not that they didn't know.