This was easier for me to explain in a brief video than by typing, so I’m just going to link the video where I explain the problem I am having:
I discovered what the problem is. The tooltip is correct (counter-intuitively.) I will upload a sample weightmap that I exported from the engine alongside the world composition overview.
The weightmaps are arranged in strips 1 tile X by 3 tiles Y. Screenshot will show what I mean. So I have to just edit the exports to match.