I ended up adding this code that makes the default post type hierarchical and populating the wp_posts.post_parent field with the author ID. The combination of these two has achieved the desired implementation of having the same slug across multiple authors.
// Set post type "post" to be hierarchical
$wp_post_types['post']->hierarchical = 1;
Source: https://stackoverflow.com/questions/10750931/wordpress-how-to-add-hierarchy-to-posts