It worked great for me, but not when there is one user, he is both an administrator and a post author.
(I deleted my other users: I had created several with different e-mails, and changed the authors of the posts)
My posts and WPSP posts lists author links returns https://www.sisla.lt/author/admin/
but not https://www.sisla.lt/rolandas-sisla/ author page link.
(I use GP PRO and WP Show Posts Pro, both latest versions)