Audience Based Visibility is Enabled
In course settings there are 3 options in Audience Based Visibility

1) Hidden from all users - Should be hidden from ALL users
2) Visible to members of the selected audiences - Should be visible only to selected audiences
3) Visible to all users - Should be visible to all users

Hidden from all users is currently not hiding the course from all users. If you have a course with enrolled Learners in the course and set the course to Hidden from all users the course is still visible by the enrolled users. If you create a new course and set the Visibility to "Hidden from all users" and then enroll Learners to the course, Learners can see the course as well. Hidden from all users is acting like Visible only to enrolled learners instead of completely hiding it from Learners.