You have to do extra work to get the hardlink deduplication in the store though:

https://nix.dev/manual/nix/2.20/command-ref/nix-store/optimi...

Unlike in FHS distros where you get some of the separation for free with usr/lib vs usr/share, most nix packages don't have separate store paths for binary vs non-binary files. At most you'll get the headers and build scripts split off in a separate dev path.