This problem seems to occur because Rotation is not taken into account when calculating Weight.
I have confirmed that it can be solved by calculating the rotation as follows.
1. Open Landscape.umap in Content Example
2. Set Soil to Landscape Layers of Foliage
3. At this time, we should be able to generate Foliage only for the Soil part, but if the rotation value is set to Landscape, it will be an incorrect generation position.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-89079 in the post.