This is a very typical soft strike, both obverse and reverse.
As such when we only see two photos, it appears that the center of the coin has significant circulation rub. In fact it is lack of strike strength, not circulation.
The 21 is unique because of the supposed high relief, but because 999 out of every thousand are softly struck.
I looked at zillions of them before I found one with decent strike.
I'd rather have a 58, or even a 55, with strong strike as opposed to a 63 with typical strike. This post offers an excellent reason why.