This problem has been known for a long while. The models used here by Metzger have such a large uncertainty and only take into account erosion due to shear. As soon as the erosion transitions from shear-based (smooth sheets) to bulk (fluidized), none of the data extends to that regime. A massive vehicle landing on the moon will definitely cause fluidization. To estimate erosion and ejecta needs far more detailed numerical methods [0].