Hello,
Apologies for the pop-up help and documentation about the course end date not being very clear.
As far as I know, the course end date is not used by any of the standard reports in Moodle, however it may be used by a custom report e.g. reporting activity for the duration of a course.
Thus, in Moodle 3.2 the setting does very little, however in 3.3 it is used for determining whether a course should be listed as 'Past' in the Course overview on students' dashboards.