The great part about that setup is my configuration contains not just my dotfiles, but also the installation of the programs themselves.
I don't use the "nix" way of configuration though, I instead have home manager symlink everthing for me. Then I can bail on nix anytime and not have to translate all my files back to yaml.
Glad programs like the above exist though for those who don't want to sink time into nix but want to reasonably track configuration.