Remote post handler posting data too early if 'Automatically save as draft when paging' is enabled

Problem/Motivation

If a remote post handler is enabled on a multi page/wizard webform, along with automatic draft saving; the $operation is seen as 'create' when the user clicks the next page button on the first page. This leads to incomplete information being sent to the remote storage.

How to reproduce

1. Create a webform with multiple pages, and elements on each page
2. Add a remote post handler and provide a url to store data to
3. Under 'Allow your users to save and finish the webform later', select 'Authenticated users' and check the box 'Automatically save as draft when paging'
4. Save and load the form, click the 'Next page' button and check the remote storage

Interim fix

I noticed that the $operation is 'update' when paging between wizard pages, so I created a custom post handler. I added the URL to both 'create' and 'update' options, and added the following code in the post handler. This seemed to fix the issue.

// I removed the namespaces and plugin annotations for brevity.
class WizardPagePostWebformHandler extends RemotePostWebformHandler {

  protected function getPostData($operation, WebformSubmissionInterface $webform_submission) {
    if(!$webform_submission->isCompleted() ){
      return FALSE;
    }
    return parent::getPostData($operation, $webform_submission);
  }

  protected function remotePost($operation, WebformSubmissionInterface $webform_submission) {
    $request_post_data = $this->getPostData($operation, $webform_submission);
    if($request_post_data != FALSE){
      parent::remotePost($operation, $webform_submission);
    }
  }

}