isn't the lack of impacts near the retroreflector due to the fact that the moon surface around the reflector is always facing earth?
"It is likely that each side of the Moon has received equal numbers of impacts, but the resurfacing by lava results in fewer craters visible on the near side than the far side, even though the both sides have received the same number of impacts."
In terms of impact gravity and atmosphere extend that somewhat. Though, that’s still not enough to make a meaningful difference.