Some sun settings lead to shadow artifacts on e.g. rocks on some maps (notably, Anatolian Plateau & the Aegean biome). This depends on shadow quality to an extent, but filtering hides the issue in general.
We can prevent the worst of these artifacts by tweaking the values slightly (image by langbart):
https://trac.wildfiregames.com/raw-attachment/ticket/6552/hide_my_Problem.jpg
Reported by: langbart