It looks like die damage to me. Keep in mind that if it were a
DDR, then it would be raised. But if the die was damaged, it would not look like part of the design. That is what I'm seeing. The bays are level with the fields. This is slightly deeper than the bays (which is the outside of the die) and not as deep as the deeper design. (the columns) The areas affected are not even in design. So I'm thinking die damage.