Not sure how I missed this part of the manual when reading through but it does mention the purpose of the vertical headlight motion!
They adjust up and down to counteract the pitching motion of the car under acceleration and braking
They'll adjust downward with a heavy load in the trunk to counteract the rear suspension compression
Page 140: Adaptive headlight range control The adaptive headlight range control feature balances out acceleration and braking processes as well as the vehicle load conditions in order to avoid dazzling oncoming traffic. Illumination of the road is optimized.