I'm not talking about the scientific inaccuracies, but rather the fact that there was a huge chance that the moon could collide with Cybertron.
Considering that Cybertron is implied to be pretty damn huge, many times the size of the moon, any damage caused by an impact with the moon on Cybertron probably would have been repaired by slave labor, which was the whole point of bringing Cybertron to Earth in the first place. Not like the Decepticons cared.
Any initial cosmetic damage to the surface of Cybertron a collision with the moon would cause is insignificant in the light of the survival of the Cybertronian race and rebirth of the homeworld.