Is it expected behaviour that National Identifier duplication check is only applied during hire?

During testing of the hire processes we noted that during the hire of a new person there is a duplicate check on the NID. This is as per design. But some testers also noticed that if the NID is edited after hiring the person, then there is not any warning or prompt to identify the potential duplicate person record.

Is this expected? It feels like an oversight.

Thanks

Mick