I totally agree with these statements...
I'd leave this to the restoration experts, but the blackish line that forms the outer edge of the crinkle (when viewed from the inside of the cover) looks a bit weird to me, and leads me to think that the triangular area that makes up the crinkle was torn away from the book and sealed back in place with glue or something. If that's not the case, it's possible something was dragged over that specific area which heavily abraded it.
I'd grade the book 7.0, but could see it getting 7.5...sweet book!