This seems to be happening more frequently over the past couple of years. As William-James88 states above, I suppose it is possible that if it's the only defect, it could still be considered a 9.6. Personally, in cases like these, I highly doubt that the original grade reflects the damage you see. Your book, as is, looks like a 9.2 - 9.4 in my opinion. Either CGC fumbled when encapsulating (and isn't taking responsibility) or it was damaged somewhere on the road after it left CGC's hands. In any case, we must all inspect CLOSELY before casting our bids, as the cgc grade is no longer (or maybe never was?) an ironclad guarantee. Look at this "9.8" which sold in ComicLink's recent auction (May 2020). Seriously, that's a 9.8?? It sold for $11,305 so apparently someone thinks it's legit (not me, i'd grade it a 7.0, that's ugly!).
https://www.comiclink.com/auctions/item.asp?id=1394426&itemType=0