"Programs provided" seems wrong for some derivations (e.g. dnsutils / dig)

[Zocker1999NET]

My case: I searched for the package / derivation providing dnssec-keygen. Using search.nixos.org finds the derviation nixpkgs#dig. For this derivation, NixOS Search lists dnssec-keygen in the "Programs provided" section. But that is not correct, because e.g. following command fails: nix shell nixpkgs#dig --command dnssec-keygen (asserting that dnssec-keygen is not already available in $PATH).
But incidentally the package bind does provide the executable I search, even through NixOS Search does not recognize it that way. Test with: nix shell nixpkgs#bind --command dnssec-keygen.