"Just a camera quirk?"
You could say that. The picture you posted was created from hundreds of pictures and spliced together. It's actually a distortion of what the lunar pole would look like if one simply took one picture of the polar region [the pole would be would be less lighted at any one time and hard to take picture of for a number of reasons]. The polar region during a month period of time of getting sun light from 360 degrees, so on any given day one a mountain side could be being lit and 28 days later the other side on the mountain could be in sunlight. They spent a fair amount of time and effort trying to splice this together, but sort like lighting someone face in sharp profile from multiple angles, then trying to splice it together so it looks like the person- or perhaps more accurately said, using the pieces which showed "most" of the person's face.