Composite Action: input variable in uses: syntax does not work

I’m building a composite GitHub action. While I can use the input variables in different places. it does not seem possible to do so in the uses: syntax, where I would like parts of the docker url to be configurable. Before I add a ticket /Feature request about it, I would like to be sure I’m not missing anything.

How I would like to use it.

  using: "composite"
    - name: Checkout
      id: checkout-scripts
      uses: actions/checkout@v3
        repository: ${{ inputs.base_repo_uri }} <- WORKS AS EXPECTED
        path: base

    - name: Image run
      id: docker-ci
      uses: docker://${{ inputs.imagetag}} <- DOES NOT WORK :(

unfortunately not in all places of the workflow file works “templatasing”/substitution.