How do I build correct Landscape HLODs in world partition?

I have gotten it to work in some simple and limited test scenarios but kept running into weird issues, sometimes re-doing the setup with the same settings would yield different results so for all I care it’s still not properly working.

Besides, how would you bake down HLODs for say a Nanite forest with tens of millions of instances with up to 2mil tris each? Legitimate question as I don’t see how this can work without blowing up the engine.