Utilizing values returned from SSM Document in a Parent/Child Document

I have a SSM Automation document which as one of its steps, calls another automation document which return two values.

I can see the output from the call to the child document back in the parent document, but I can't seem to find a way to reference it.

Outputs
ClientToken
38014768-65e1-4a3a-821d-9xxxxxxxxxx

ExecutionId
38014768-65e1-4a3a-821d-97acxxxxxxxxxxx

Output
This is a message to pass into the updatefinding step, SUPPRESSED

Status
Success

If the output was in the parent document I would have used {{ParentDocumentStepName.outputvalue}}, but when I try that as {{ParentDocStepWhichCallsSubDocument.outputvalue}} it doesnt seem to resolve. Does anyone have any suggestions for things to try?

Here is my parent document:

description: |
  ### Document Name - TestParent

  ## What does this document do?
  This is the parent for a test of Parent to child testing

  ## Input Parameters
  None

  ## Output Parameters
  None
schemaVersion: '0.3'
assumeRole: ''
mainSteps:
  - name: Remediation
    action: 'aws:executeAutomation'
    isEnd: false
    inputs:
      DocumentName: TestChild
      RuntimeParameters:
        AutomationAssumeRole: 'arn:{{global:AWS_PARTITION}}:iam::{{global:ACCOUNT_ID}}:role/SO0111-ConfigureS3ServerAccessLogging'
    outputs:
      - Name: remediationOutputMessage
        Selector: $.Payload.RemediationResultStatus
        Type: String
      - Name: remediationOutputStatus
        Selector: $.Payload.RemediationResultMessage
        Type: String
  - name: UpdateFinding
    action: 'aws:executeScript'
    inputs:
      Runtime: python3.8
      Handler: script_handler
      Script: |-
        def script_handler(events, context):
          print(events)
          return {'message': 'Hello'}
      InputPayload:
        message: '{{Remediation.remediationOutputMessage}}'
    description: Update finding
    isEnd: true

And here is my Child Document:

description: |
  ### Document Name - TestChild

  ## What does this document do?
  returns a json object fixed for testing

  ## Input Parameters
  * AutomationAssumeRole: (Required) The ARN of the role that allows Automation to perform the actions on your behalf.

  ## Output Parameters
  * Remediation Result Status
  * Remediation Result Status
schemaVersion: '0.3'
assumeRole: '{{ AutomationAssumeRole }}'
outputs:
  - RemediateTargetBucket.RemediationResultStatus
  - RemediateTargetBucket.RemediationResultMessage
parameters:
  AutomationAssumeRole:
    type: String
    description: (Required) The ARN of the role that allows Automation to perform the actions on your behalf.
    allowedPattern: '^arn:(aws[a-zA-Z-]*)?:iam::\d{12}:role/[\w+=,.@-]+'
mainSteps:
  - name: RemediateTargetBucket
    action: 'aws:executeScript'
    description: |
      Returns a fixed json object
      ```
      {
            'message': 'This is a message to pass into the updatefinding step',
            'resourceBucketName': 'bucket1',
            'LoggingBucketName': 'bucket2',
            'status': 'SUPPRESSED'
      }
      ```
    timeoutSeconds: 60
    isCritical: true
    isEnd: true
    inputs:
      Runtime: python3.8
      Handler: lambda_handler
      Script: |
        import json
        def lambda_handler(event, context):
          return {
              'message': 'This is a message to pass into the updatefinding step',
              'resourceBucketName': 'bucket1',
              'LoggingBucketName': 'bucket2',
              'status': 'SUPPRESSED'
          }
    outputs:
      - Name: RemediationResultMessage
        Selector: $.Payload.message
        Type: String
      - Name: RemediationResultStatus
        Selector: $.Payload.status
        Type: String