Event registration, "Same email address" checked, is ignored for admin-created registrations

Normally when "Same email address" is checked for an event, admin or user can create multiple registrations that end up tied to the same contact. This is working properly for the user-submitted online registration form, and for the administrative "New Event Registration" form. However, if we are viewing the Events tab of the user's contact record and attempt to use either the Add Event Registration" button or "Submit Credit Card Event Registration" button, after the form is completed and submitted, it rejects the submission with "This contact has already been assigned to this event." So this logic seems to be ignoring the allow_same_participant_emails setting for the event.