The CCC wrote:.
Except that we have many witnesses to the fact that he had the plates.
No we don't.
What we have are witnesses to the fact that Joseph Smith had something.
Not one of the witnesses could testify that what Joseph Smith showed them was actually an artifact created 1200 years before, and in fact we know from the Kinderhook plates that there were those who were able to fool people with clumsily made up props even well into the last century.
Given the years Joseph Smith spent conning people into paying him for elaborate treasure hunting rituals, the fact there were so many contemporaries willing to believe any ridiculous story about treasures and supernatural interventions, the years Joseph Smith had to create all sorts of stories about the early American natives, the four years he had creating and telling a story about an angel showing him plates, the complete lack of any physical evidence to connect the Book of Mormon people with any known past peoples from the Americas, the absurdity of the stories within the Book of Mormon describing the manner in which these imaginary people's came across the ocean, the lack on any DNA evidence supporting such an immigration, and so on; it is clear that what Joseph Smith showed people was just a prop.
No missionary I have ever shown my old Latin leather bound book on astronomy has ever denied their testimony of seeing the first Greek Book of Mormon version owned by Orson Hyde.