Business Rule 'No Duplicates' on sys_documentation throws an error when localization is set to en.AU

When attempting to set the System Localization (glide.sys.language) system property to en.AU and then trying to update the default value of a dictionary entry, the business rule "No Duplicates" on the sys_documentation table throws the blocking error:

"A documentation record with the same values of Table, Element and Language fields already exists"

1. Navigate to System Definition > System Localization
2. Set the default system language to en.AU
3. Go to a dictionary entry of Type "String" and set or clear our the default value
Example change_request.category

The BR "No Duplicates" on sys_documentation will run and trigger the error:
"A documentation record with the same values of Table, Element and Language fields already exists"

Note: After resetting the property you have to log out and back in, as the user session saves the set language.

This is expected behaviour. The System Localization property glide.sys.language (the default language field in the UI) accepts only a two-character value. The en.AU value should be set for the glide.system.locale value. In the UI, this is the field following the default language property field.