Nix / NixOS

Yes I know that there are workarounds for them to set to use the flake inputs but still.. I have set nixpkgs version to 23.11 stable release and that's good, but if I try to use nix shell, nix profile or even nix-env, they all seem to use the latest master/unstable branch to install the packages by default.

Just want to know why aren't they just default to use whatever is defined in flake.nix file? will it be implemented to use it by default in the near future?

Reason as to why I am asking -> This is what I am using to match nix shell and flake inputs, but as you can see they are just workarounds, plus seem to cause more errors and whatnot, plus by ideology one shouldn't need to specially define it to use some version when everything is already defined.