I agree with the over polished die theory. But that is die abrasion rather
Die Deterioration. Deterioration is normal die wear on the overall design of the die. Die abrasion is localized/intentional removal of die design from over polishing. Usually you see this in the direction of the rim areas. This one was done to cover a clash/clashes not affecting the mid devices on the die in the center.

We sometimes see this on Lincoln cents.