why the fucking fuck is `nix flake update` followed by `sudo nixos-rebuild switch --flake .#mylaptopsredactedhostname` not updating my systempackages

i can plainly see vscode is at 1.86.2 in the nixos-unstable branch, and my flake.nix is using that branch, and yet I'm still stuck on 1.85.1

#nixos #nix #nixflake