It appears that the following courses are the same with respect to which aggregation pipeline is being discussed:
For example, Lecture: The $bucket Stage and Lecture: Facets: Manual Buckets are lectured by different instructors but discuss the same $bucket stage. Perhaps this is intentional to provide students with more content.
I’ve completed this course but just bringing it everyone’s attention in case it causes any confusion. It’s also been reported to the University.