/page/?xxxx=John Foo or /page/?xxxx[]=John Foo will show posts by the author whose username is John Foo. If no such author exists, no posts will be shown.
/page/?xxxx[]=John Foo&xxxx[]=Peter Bar will show posts by both the authors whose usernames are John Foo and Peter Bar. If one exists, his posts will be listed; if none exist, no posts will be displayed.
Note that if the URL parameter is missing or empty, all posts will be listed and no author filtering is done.
Makes it seem that we can only find the username as a constant, but not as a variable.
How can we derive the username from this url 'hidden link'?
I would create a custom shortcode ( ref: https://codex.wordpress.org/Shortcode_API ), that can get the current URL, extract the last part (i.e. /brandon/ ) to get the username, and then return that username.
You can then set the view's post-author filter to get the target author from the view's shortcode attribute 'author', as shown in the attached screenshot.
And the output of that custom shortcode can be passed in the view's shortcode, for example: