Is slowing down justifiable in this this situation?

Why?

Pedestrians are walking along a narrow shoulder close to the roadway, while a car approaches from the opposite direction. Slowing down makes it easier to leave safe clearance and react if someone steps into the road. Your speed must suit the actual conditions, even when you are below the speed limit.

art. 19 ust. 1 i art. 23 ust. 1 pkt 1 Prawa o ruchu drogowym