bug: nixpkgs settings can't be set in multiple places, unlike on nixOS configuration

[stereomato]

Are you following the right branch?

• My Nixpkgs and Home Manager versions are in sync

Is there an existing issue for this?

• I have searched the existing issues

Issue description

Basically, right now I want to set overlays and config on different places, to keep stuff that's related to each other close. I can do this on NixOS configuration:

nix-repl> config.nixpkgs.overlays
[
  «lambda @ /nix/store/hdhxrzjcw5c3xddrq24f8hcvfm1h60q4-source/machines/common/imports/overlays.nix:4:3»
  «lambda @ /nix/store/hdhxrzjcw5c3xddrq24f8hcvfm1h60q4-source/machines/Taihou/kernel.nix:3:3»
]

but not with home-manager:

nix-repl> config.home-manager.users.stereomato.nixpkgs.overlays   
[ «lambda @ /nix/store/hdhxrzjcw5c3xddrq24f8hcvfm1h60q4-source/users/stereomato/imports/overlays.nix:3:3» ]

I set my overlay and (and nixpkgs.config too, which also doesn't work) on two different files:

• https://github.com/stereomato/nixos-setup/blob/main/users/stereomato/imports/overlays.nix
• https://github.com/stereomato/nixos-setup/blob/main/users/stereomato/pkgs/internet.nix (not yet committed, but I applied the overlay there)

Now, I do have home-manager.useGlobalPkgs = false because I want to keep nixos nixpkgs and home-manager nixpkgs separate.

Maintainer CC

Maintainers aren't listed, so I'll tag:
@rycee
@emilazy

System information

- system: `"x86_64-linux"`
 - host os: `Linux 6.11.5-zen1, NixOS, 24.11 (Vicuna), 24.11.20241025.18536bf`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.24.9`
 - nixpkgs: `/nix/store/wb6agba4kfsxpbnb5hzlq58vkjzvbsk6-source`