Earlier quoted context omitted.
Without knowing all that much, I know that Earth was much more massive than Mars even before Theia impacted. I assume with the extra energy available, it would be much more likely to melt all the crust. Also, our plate tectonics is still going on, so any evidence of a thin area of crust would be erased by now.
also it's interesting that the crust of the moon have differences between far and near side. I read somewhere that this could be explained very easily with a low speed impact of a second small moon when the moon was very young.
There was a recent paper proposing that the near side of the moon looks melted because the surface of the Earth was temporarily about as bright as the sun for a while after the impact.