In OrgSync, deferring a form submission is the same as putting it on hold. This status is designed for form administrators that want to remove the "pending" status of a form but they aren't yet ready to approve or deny the submission. The submitting user is not notified when their submission is deferred.
Re-opening a form holds an entirely separate purpose. This sends the submission back to the user and it allows them to make changes and re-submit. They will be notified when you re-open their submission.