Its in the middle of the spine and runs into the cover, not sure how it would have happened post slabbing. Your logic is sound though, not sure. The only real slab damage I have seen is inner well indentation, that happens very frequently. I am sure someone has a scan of the 181 , we can pull the grader notes There should be none for that copy(Like most 9.8-10) unless they call out a stress line then we are really onto something, Either way is a noticeable defect and the Professor's 9.8 is a superior copy hands down at a fraction of the price,