When you select the visualisation by academic year you will see the courses planned for a given academic year (i.e., second-year courses of a.y. 2019/2020 are the courses that should be taken by the students who enrolled in year 1 in a.y. 2018/2019)
When you select the visualisation by cohort (year of first enrolment) you will see the courses planned for the students who are currently enrolled in year 1 (i.e. students belonging to cohort 2025/2026 will see second-year courses offered in a.y. 2026/2027)