1) What happened
Baked directional light produces artifacts on shadowed side of primitives

2) How can we reproduce it using the example you attached
1. Open scene 1 in attached project
2. Bake
---> See dark spots on shadowed side of primitives

This goes away for realtime light. Also this applies only for Lightmapping > General GI > Directional Mode > Directional. Other modes don't have this issue.