Subdir ignored in `channel/subdir` specifier

[jonashaag]

conda create -n xxx 'conda-forge/noarch::git'
...
PackagesNotFoundError: The following packages are not available from current channels:

  - conda-forge/noarch::git
...

mamba create -n xxx 'conda-forge/noarch::git'
...
  added / updated specs:
    - conda-forge/osx-arm64::git
...

This also applies when installing from environment.yml files.