saving body text programatically with a Media tag doesn't work with the view mode

I tried to create a node programatically with a media tag in the body (this was using Migrate BTW).

I used this code to create a Media tag which I then put in the body text:

  $data = array(
    'fid' => $file_entity_fid,
    'type' => 'media',
    'view_mode' => $view_mode,
    'link_text' => NULL,
    'attributes' => $attributes,
  );

  return '[[' . drupal_json_encode($data) . ']]';

This works up to a point, but when $attributes is an empty array, the view mode is ignored.

If I then edit the node in Drupal and re-save it, the view mode then applies.

This seems to me to be caused by the same thing that causes #2422153: View mode classes accumulate when changing image view mode -- it appears that the CSS classes for view modes are added to the tag, rather than deduced from the view mode.