Cool indeed. Lucky accidents do happen. You could add a pop of the internal grass where the trees are on bare rock to. Set it to follow the rotation of the terrain, and make the underlying grass object a little smaller by reducing XZ to 0.5-0.6 or so (you get 5-6m blocks of grass then, which are less prone to float), and maybe make the stems longer (0.5m, and sink them a little, say 0.2m). Give them a fractal color followed by a transform shader set to world/final position, pulled into the color input of the grass' default shader.
Mask the pop by max slope, and perhaps some fractal.
