I'm with you. But I think of it more in terms of eye appeal rather than rarity. If that same fragment stayed on the anvil die, even in the same position, the image would have been mashed by this strike reducing the clarity of the secondary image struck into the next. Same error, same orientation, fuzzier imagery equals less appealing. IMO the appeal lies more in the clarity of the secondary image. It gets some bonus points in my eyes for the central location, but really if that same strike through happened anywhere on the coin it would still be very desirable.
