Disabling Spinner in V2

I’ve noticed the following code in the mwEmbed project for the loading spinner:

var spinnerIsEnabled = !mw.getConfig('LoadingSpinner.Disabled');
// Support new standard config.plugin representation:
if( mw.getConfig('loadingSpinner') ) {
  var config = mw.getConfig('loadingSpinner');
  if( config && config.plugin === false ){
    spinnerIsEnabled = false;

This suggests to me that since getConfig() is merely looking at the window.preMwEmbedConfig object, the property ‘LoadingSpinner.Disabled’ will need to be set on the window.preMwEmbedConfig object in order to disable the spinner. However, the on-page JSON configuration for a V2 player does not modify the mwPreEmbedConfig in any way.

Am I missing some other code which allows users of the V2 player to disable the spinner via JSON, or has this not been implemented for control via JSON?

Thanks in advance for any assistance you can provide.