ZA - Unable to end date Reason for Absence Attendance Type

Hello

We currently have an Absence Attendance Type of Religious Observance Leave.  In the past, the HR dept would maintain a list of days allowed for the various religious observances (EG: Maha Shiv Ratri 2 ; St Michaels Day ; Channukah (1st Day) ; Islamic New Year 1st Muharram) and these would be captured in the Reasons area of the form.  It has now been decided that the maintenance of this list of days is too onerous and they wish to put in one reason only (Religious Observance).

The problem arises when I try to either end date or delete the Reasons.  I get a message "APP-PAY-07060:  You cannot delete a reason used for an employee absence".  This makes perfect sense if trying to delete but I do not understand why I cannot end date for a future date, where the element has not been used after that date.