I decided to make a sub-task of a Phabricator ticket marked as Security (T158473). To do this, I clicked on the "Edit Related Tasks..." option in the right side menu, then "Create Subtask". I did not modify the suggested subscribers or tags. When the ticket was created, it was not automatically protected as a security issue and users subscribed to the tagged projects received an email notification with the description I provided.
As I attempt to recreate this, I see 'Security' as a tag when I go through the same steps. On save, it is not protected. T175071: Test ticket — please ignore