Cannot use multiple $file variable in Resources section of serverless.yml

This feature request indicates that it should be possible to include multiple files in the Resources section. I want to do this to better manage a large file with hundreds of resources in it.

However, doing this

    - ${{file(1.yaml)}}
    - ${{file(2.yaml)}}

Results in a template with the Resources key set to a list, which looks like

"Resources": [
      "Resource1": {
        "Type": "AWS::Logs::SubscriptionFilter",

Which fails when the template is uploaded to CloudFormation:

  Error --------------------------------------------------
  The CloudFormation template is invalid: Template format error: Any Resources member must be an object.

What is the proper way to use this feature? I’ve tried this dozens of different ways in multiple versions of serverless and using $file in the Resources section always results in the variable not being interpreted, interpreted wrongly as in this bug report, or producing invalid output in the CF template.

Looking at those bugs reports, I’m not sure this feature works…