I just tested some cases with the latest version of the Workflow application and I received the emails.
If other emails are sent (also Share by email feature), then I would check what does the shortened variant implies, to be sure that the email sending process was not also shortened.
These emails are sent immediately by the Publication Workflow Application and do not depend on the notification frequency configured in XWiki. On my system, they arrived within two to three minutes, although the actual delivery time may vary depending on the mail server configuration, the email queue, and other messages being processed by the wiki.
As shown in the following screenshots, email notifications are sent in all the documented cases, although the wording in the emails differs slightly from the documentation.