How "No Holders" appears in Position Hierarchy?

Hello, does anyone can help advising under what conditions will "No Holders" appear? We only know it will happen when the existing user license holder is disabled for his/her user account, given that he has been assigned into the position hierarchy. However, we don't know how it actually happens and when it will trigger this happened.

Currently, When "No holders" is shown, the Name column (we use this to store the staff ID) is appeared and we found it useful to track the history. We don't want to delete "No holders" record, but it gives a hard time as we don't know how to achieve this status, so it ended up having all old holder name records which mix up with the existing ones. We want to find out how to name all those old records into "No Holders" for easy checking while keeping their staff IDs in the hierarchy as audit trail.