This post explains the USP Pro General setting, “Use Registered Author”. In a nutshell, this setting determines whether or not registered usernames are used for submitted posts. Read on for more information..
This setting is located in the plugin’s General settings:
General settings ▸ User Settings ▸ “Use Registered Author”
When this option is enabled
If the user is logged in, their username will be used as the Post Author.
If the user is logged out, the Post Author will be either the registered username (if the form is a registration form) or the “Default Assigned Author” (located under General settings ▸ User Settings).
When this option is disabled
If the user is logged in, the “Default Assigned Author” will be used as the Post Author.
If the user is logged out, the Post Author will be either the registered username (if the form is a registration form) or the “Default Assigned Author” (located under General settings ▸ User Settings).
To get a better idea, you can see how this setting works by submitting a few test posts with the option enabled, and then again with the option disabled. For each test post, take a look at the Post Author to see the difference.