The sorting to the users related list will be whatever sorting the admin had when they came to the page. You can create a new View or edit the existing one to add in the Created Date to make it available for sorting. If the admin then chooses to sort by Created Date ascending by clicking on the column header, they will see the most recently created users at the top of the list. See the help document, Sorting List Views.
Here is an example that shows it. Note the down arrow on the Created Date column showing that the users are sorted by Created Date. Also, note the Edit and Create New View links. Click those to edit or create a new View. You can create a View that is shared with all users or specific users if need be. See Creating Custom List Views for more information.
There is one other possibility. If the organization has more than 2 million users, the users list view cannot be sorted according to this help doc:
Starting in Spring ‘13, list views for the Users object in organizations that have more than two million users cannot be sorted.