oneOf with discriminator on path

Start with the minimal OpenAPI example in the issue and review how discriminator validation is handled for request bodies and path parameters. Check the project's validation entry points and tests for oneOf and discriminator behavior; done should clarify or implement the expected relationship between the path item_type and the selected schema.

As all different types of request bodies should be processed by the same function, I was hoping to do something the following minimal example:

  /api/{item_type}:
    post:
      parameters:
        - in: path
          name: item_type
          required: true
          schema:
            type: string  
      requestBody:
        $ref: '#/components/requestBodies/object'
        required: true
      responses:
        '201':
          description: Item created
components:
  requestBodies:
    object:
      content:
        application/json:
          schema:
            oneOf:
              - $ref: '#/components/schemas/Movie'
              - $ref: '#/components/schemas/Program'
            discriminator:
              propertyName: item_type
  schemas:
    Movie:
      type: object
    Program:
      type: object

Essentially, I want one function, to parse all item_types, but still ensure validation based on item_type in the path. However, I can create a Movie with the properties of Program.
Is this not the intended use? Or is there no discriminator validation on parameters specified in the path?

Thanks in advance.