Hierarchical Instanced Static Mesh requires 2000 tris to work

Hi there:
Been using Hierarchical Instance for my project, and find this particular issue:My Hierarchical Instance (with Lod) seems only to work when the Base Mesh (LOD0) is larger than 2000 tris.
I understand this setting might be intentional, since meshes under 2000 might not need a Lod. But in my case, I need to keep the mesh low, and only swap the material for the other LOD. In the image I have attached, both group has the same LOD1, but different LOD0 with 209 tris and 2496 tris respectively. My engine version is 4.20.3, if this issue is fixed in the later engine version then plz let me know as well. Thanks

Problem solved. For anyone wants to know this, there is a command line you can put in the editor"foliage.MinVertsToSplitNode 0", it controls the accuracy between culling and LOD accuracy and culling and CPU performance. Basically you define the minimum verts of a mesh that will be LODed. So if you put 0 it means everything can have a LOD, 2000 means meshes that are more than 2000 verts will have LODs. I think the default number is 2000.

If anyone has better understanding of this plz tell, I could be wrong.