Active Audit Events - CM9.4

Hi,

In CM9.4.457 Patch 1 when a User Type Knowledge Worker looks at the Active Audit Events for a record, the username of whoever did an action is displayed as '*******'.

For user types Record Manager or Administrator the username is displayed as is expected (see attached screenshots)

I've looked over the permissions for Knowledge Worker but can't see anything that should be selected to avoid this. 

Does anyone know what the issue is, or is this expected behaviour?

Thanks

Michael