*Almost any system can attempt that. Nix lets you pin your whole dependency tree, and Nixpkgs includes facilities for managing the configurations of many appli

*Almost any system can attempt that. Nix lets you pin your whole dependency tree, and Nixpkgs includes facilities for managing the configurations of many applications, including integrations with their plugin systems that explicitly manage external runtime dependencies, like stuff your vim configuration might call at the CLI. Without that stuff, reproduction can often fail in practice. And in the case of NixOS, you can also reproduce things like running services and their configurations, which users exist, etc. Those are OS and configuration management features, not package management.