When listing prerequisites, we list only those which may not be second-nature to the student. For example, when learning how to sketch curves using stationary points, you must be able to plot the turning points on the coordinate plane. However, a calculus 1 student has been plotting points for years, so this prerequisite should not be mentioned. Fresh skills, such as finding the derivatives of polynomials, should be mentioned. That way, students may review that material if they are struggling. Listing prerequisites is a way to inform the student what may be holding them back.
For puzzles, we do not list the prerequisites, since often the fun of solving a puzzle is figuring out which tool to use. However, in order to introduce a puzzle at the right time, the curriculum developer must know the prerequisite skills. Therefore, we must create a method to show prerequisites to developers but not students.