World Position Offset Only Affecting the Z-Axis when applied as a Material to a Landscape

When utilizing World Position Offset on Landscapes, the VertexNormalWS only pushes vertices in the vertical direction. Even if you are to sculpt an aggressive slope on the landscape, the vertices are pushed only upwards.

With the same material applied to a Sphere the vertices respond as expected and are pushed in the correct direct based on their WS Normal position.

This almost seems expected as the entirety of the landscape defaults to facing upwards so pushing/pulling vertices will only affect the vertical direction, but this is a guess which needs some clarification.

1. Download and open attached project.
2. Open 'T_Grass_Mat_Instance'
3. Increase the 'Offset Amount' value to a high number.

Outcome The vertices on the landscape are pushing only in the vertical direction.

Expected The vertices are pushed in the correct direction based on the Vertex Normal WS of any one vertex on the landscape. e.g. A steep cliff face the vertices would push/pull out away from the sloping geometry.