A. Landscape doesn’t perform well on mobile, not to mention mobile VR; B. Tiled renderer can not cull triangles outside of FOV, plus UE4 doesn’t have distance culling for surfaces. Thus in order to cull terrain outside of FOV (or occluded parts) and use LOD, it has to be cut into pieces.
Like I said, this is the only way to have terrain, that looks and performs well, on mobile/mobile VR. I already use it and it works wonderfully. The only headache is setting it all up in UE4. So a terrain plugin that does all that for me would be a greatest gift :o