My experience differs: It is the common situation that the theory is taught in the lecture, and then each week you have to do quite some exercises to implement all the newly learned data structures in code (lots of work to do each week :-) ). So, if you forgot such a "detail", the code to write for next week simply won't work - 0 points.

This way, it is rather unlikely that you will forget such a "detail" in the forest of new things to learn. This statement in particular holds for students who had done pretty well in DS as the one you are talking about.