Learning Authors and Learning Administrators have the ability to create dynamic curriculums which will require students to complete courses added at a later date even if they completed the original curriculum. This setting can be found by editing the curriculum in the Curriculum Properties tab and checking off the "Dynamic Curriculum" checkbox (see below):
Any time a curriculum is made dynamic, all new and required courses added afterward will be required for all existing students. If any course is added to a dynamic curriculum, all enrolled students who have already completed the curriculum but have not completed this new course will be reverted to Incomplete in their transcripts.
Conversely, if a new course is added to a non-dynamic curriculum, any students currently set to Completed would not be responsible for completing this new course and their curriculum enrollment status would not change. Making the curriculum "dynamic" after a new course has been added in this instance will not automatically revert completed students back to Incomplete.