Heya!
Super excited about this perticular feature " New: Added bUseVertexNormalForHemisphereGather Lightmass primitive setting for foliage static lighting, in cases where artists want foliage lighting to match the underlying terrain. "
As I’ve had alot of trouble with this and just as I spent a whole week trying different solutions I saw this in the patch notes! 
I just can’t seem to find where I’m supposed to toggle it. 
I’ve tried looking in the staticmesh - foliage settings - directional light - skylight - world settings etc.