If a student has a non-existent article in the students table, does not appear as a redlink to that page, and trying to add another non-existent title for that student will result in nothing happening. (Existing articles can be added in any number, but only one non-existent article can be added per student.)
If the non-existent article is subsequently created, it remains unlinked in the students table. Attempting to re-add the same title *after* it has been created results in a database error. For example, when I attempted this on test2 wiki :
Function: EducationProgram\ArticleStore::insertArticle Error: 1062 Duplicate entry '7-903-Crazywaht' for key 'ep_articles_course_page' (10.64.16.27)
Non-existent articles added for students should appear as redlinks, and they should become normal links if the target page is created.