It only works well when the scale function is a constant. It's useful if you want to change the sizes of all the stones in a network because you can have many different layers controlled by a single node which acts as a master scale multiplier. This might be useful when sharing a node clip between different scenes.
It's not really designed to let you vary the scale of the stones in different parts of the terrain. That doesn't work well because the scale function works by resizing the texture space, and this basically warps the stones in unexpected ways.
I do have plans for updating this shader in future with a better way to vary the scale.
Matt