The scanner hardware does not have that much resolution in real life.
Software is called upon to interpolate what's happening between samples.
Therefore, you have to take what you get with some degree of suspicion. I can't guess what we're staring at. The 'fat pixels' are not due to pixel replication on my part, but I can't speak for the scanner's interpolation software. Notice that there are several 'depressions' in the pattern. Go to the next scanner oddity .