redoc Plaintext examples are ignored

The following example is a reduced version of my (afaik) valid OpenApi 3 file defining a request body with both application/json and text/plain mimetypes:

openapi: 3.0.3
info:
  title: 'Test API'
  version: 1.0.0
paths:
  /users:
    post:
      summary: 'Missing CSV examples'
      description: 'This demonstrates missing csv examples'
      requestBody:
        content:
          application/json:
            schema:
              type: object
              properties:
                records:
                  type: array
                  items:
                    $ref: '#/components/schemas/person'
          text/plain:
            schema:
              type: string
              example: "This is a Test"
        required: true
      responses:
        '200':
          description: 'Placeholder response'
components:
  schemas:
    person:
      required:
        - person_id
        - name
      type: object
      properties:
        person_id:
          type: integer
          description: 'Person identifier in source system'
        name:
          type: string
          description: 'Person name'
      example:
        person_id: 1
        name: 'Hello World'

The official Swagger Editor accepts the plaintext example: swagger-editor