nix-channel --update pulls irrelevant substituter?

[peterbecich]

Describe the bug

My ~/.nix-channels are:

https://nixos.org/channels/nixos-22.11 stable

My /etc/nix/nix.conf includes:

trusted-substituters = https://cache.nixos.org https://hydra.iohk.io 
substituters = https://cache.nixos.org https://hydra.iohk.io 
trusted-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY= hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ=

There is currently an issue with the IOHK substituter.

nix-channel --update stable yields:

unpacking channels...
warning: error: unable to download 'https://hydra.iohk.io/4lya937qxakkxq07lwj2sxgs6j2g43j6.narinfo': 
  Timeout was reached (28); retrying in 327 ms

The issue is solved by removing the IOHK substituter and restarting the Nix daemon.

Expected behavior

Can nix-channel --update ignore the failing substituter?

Is it necessary for nix-channel --update to use all substituters?

Additional context