Stamp Smarter database has almost 2000 reviews, most where the sellers were contacted. The percentage of sellers that were willing to improve their listings is
36%. This seems pretty firm, quantified evidence that about
1/3 of all sellers are willing to update or change a listing.
Less than 1% of the reviews are cases where the listing was in error in favor of a buyer; 'mistakes' and 'errors' almost always favor the seller. Many people, for various reasons, list stamps as the more expensive variety.
I would also add that the original poster calls out a listed
collection. It is generally understood that collections contain stamps which may or may not have been reviewed by the seller. Few people have the time or expertise to check every stamp in a collection.
ebay is full of misidentified single stamps; in my opinion is more critical to fix these as opposed to trying to address the larger mixed collection listings.
Don