I agree, but it doesn’t have to be pass or fail. A result of “Unable to render an opinion” is available for autographs that are somewhere in the middle.
It isn’t the same. When an item receives a result of Questionable Authenticity”, it’s stated on the letter that they’re of the opinion that the item isn’t authentic.
As a practical matter, a signature in a known signed edition might be presumed to be real by collectors (barring known autopen issues), but once it is cut out of the book then it's on its own.