I agree that the base cloud color from above is strangely drab grey where it should be a pure white with bluish shadows around the edges. I don’t think inversion is the answer, as the clouds to clearly model directional light and shadows, and inverting them would completely break it.
This feels like a tweak to the cloud shaders is required when seen in full sunlight (they look great at low angle times of day, or from below) to boost out the grey and make the shadows look more accurate