grammar - Does a name go before or after the noun it modifies?

The sentence

The user “john_smith” has been registered; go to the “User Profile” tab to view the user’s details.

reads more naturally to me than

The “john_smith” user has been registered; go to the tab “User Profile” to view the user’s details.

but I’m not sure why. In particular, it seems wrong for john_smith to go before the word user, whereas User Profile can go either before or after the word tab (although it seems to flow a little better when it’s before).

What rules of grammar apply here?

UPDATE 5/19/2018: I’ve changed “John Smith” to “john_smith” to help clarify that it is supposed to be a unique “username” assigned to a new user.