Username Deletion Requierement, reuse?

I have a requirement to implement the username for an application for login purposes, the requirement specifies that the registry asosiated with the user/username in the database must not be deleted, wich is a standard, never the less, the requierement specifies that the username once marked "deleted", must be available to reuse. So the implementation what it does it changes a flag booblean "deleted" to true, so when login is triggered, the query verifies that the username exist and the boolean "deleted" is false. Would this be a good practice? I would like to know opinions for implementing username reuse.