[mturmon]

It seems like you have re-discovered why segmenting the lunar image and shifting it backwards in time, to align the three color planes, was not done. They don't have the information to fill in the resulting gap, because it was occluded. In a very real sense, they have nothing to put in those pixels.

If they had wanted to do it, they could have. The ephemeris (i.e., basic imaging geometry relating to the location of Earth, Moon, and camera) will be very well-known. That bread-and-butter image processing is no problem.

The historical context here is that NASA centers, prominently JPL, were among the inventors of what became digital image processing (https://en.wikipedia.org/wiki/Digital_image_processing#Histo...).