mkDerivation is in qt5 attribute set, not libsForQt5. Though adding wrapQtAppsHook to nativeBuildInputs should work with stdenv.mkDerivation (see Qt: Do not require mkDerivation by ttuegel · Pull Request #71089 · NixOS/nixpkgs · GitHub).
And we can add this use case to the lists of reasons I do not like libsForQt5.callPackage.