Landscapes don’t work that way. They arent analytical meshes where you can add more detail only where required.
Use Blender with the dynotopo brush. Youll be a thousand times better off.
Reducing the x/y scale of a landscape will change the vertex density of the mesh - and worsen your perfoemance.
Default is 1m per vertex at 100 scale.
A value of 50 puts a vertex every .5m instead.
Perfoemance wise you deop about 8ms or so, which isnt really worth it.
In short. Your diatribe above won’t do anything for mesh subdivisions. The verts are always at a fixed distance.