Can't Update Override Daily Duration on Absence Type

Summary:

We have an absence type set up with Illness or Injury as the pattern, and on the Display Features for Override Daily Duration, this was originally set up as Not Enabled for employees, managers, and admins. We have a requirement to allow that to be updated, but when I go into Update or Correct mode, I can change all the other Display Features values (such as Schedule nonworking days), but I can't change Override Daily Duration. Is there a way to update this?

Content (please ensure you mask any confidential information):

All our other absence types are set up as Generic Absences, and the Override Daily Duration is editable on all of them. I was wondering if this restriction to edit the Override Daily Duration might have to do with the absence type pattern of Illness or Injury. I could find nothing in the Absence Management Implemenation and Using guides about a restriction.