I was highlighting the difference in ease of use. While you can do anything in nix and provide versions you want, it's not as nicely wrapped as asdf. For some things supported by asdf, like elasticsearch, nix requires a lot more work. It's a bit like the old dropbox-via-rsync comment - it's true you can do these things through shell.nix, but that's not why people use asdf. There's space for a flake wrapper which will make things much easier.