AJAX post on node edit page
The Drupal Ajax call is not affected by event.preventDefault in the above code, as neither the Click() or on('click') Jquery function gets executed on Drupal Ajax call.
Please refer the link below 

Jquery gobal ajax events

In the above code the ajaxSend()
 function can be used to stop the Ajax call even before getting started. And use event.preventDefault in the function to stop the Drupal Ajax Call before getting executed.

For Example:

$( document ).ajaxSend(function() {
  event.preventDefault();
//add you code here.
});

Please check if this code will work in the function your calling, i am not sure (may work) or else call this code directly in you attached JS file.