If a Landscape Grass Variety has a low density, it will not align correctly to Landscape. Groups of rocks, sticks and other horizontal meshes will look like they are floating or sticking out of the landscape.
This can mostly be observed near the edges of a sculpted cliff or in similar areas where the angle is changing strongly.
The only workaround is to increase the density of the Grass Variety or not have any sculpted cliffs in the landscape.
Check the attached/linked project to easily see the issue: