Just a few parameters. And they don’t “tile” the complete terrain, there are many meshes… there could be some local tesselation (if they use it at all) but they use multiple meshes, when you approach a mountain. These meshes are stacked, and the boundaries give issues. See this topic and this topic. But the reason we SEE that happening now, is distance… Just like the trees, terrain LOD stays at 50, also when the slider is put on LOD-200. Policy, or… simple bug. Both is possible. I think the whole thing could be solved with a hotfix. When it’s policy… guess… the fix for PC will be Tuesday, 3-August 
they will want to keep the 2080 and 3080 users…