The rest of the die was showing die scratches on it at one time. But now the bay is preventing of the flattening of the die scratches you are seeing. Probably others will also be seen on other bays, but that one bay has a lot of protection on that bay. (Die scratches flatten first on the open fields. Then the next to devices they last a lot longer. But inside of a protected area, they remain the longest there on the die)