PCG using texture to limit placement area - how?

I have a mesh based terrain, which has some “lakes”. I made a mask texture, which defines where vegetation/rocks/etc. need to go (pink arrow points on the area of the mask I am working with currently):

This is the PCG graph (so far):

If I turn off Absolute Transform (default):

I get this:

With Absolute Transform being on:

I am guessing that Absolute transform “on” means texture is projected as intended, based on UV map of the mesh and with “off” it squashed to fit the PCG volume?

Why do I have only a few non-black points and the rest is black?

How do I make it where in the white pixels of the textures points are 100% scale (with random +/- margin) and make scale to go down as pixels getting into black (also with random +/- margin)?

Thanks