An article by Daniel H. Ludlow reminded me of another evidence that Joseph translated two separate sets of plates.
1. The abridged plates which Joseph took from Moroni's stone box and translated in Harmony. Before leaving Harmony, Joseph gave the abridged plates to the divine messenger who took those plates back to the Hill Cumorah. Joseph identified the messenger as one of the Three Nephites.
2. The small plates of Nephi which Joseph translated in Fayette after the messenger brought those plates from the repository in Cumorah. This messenger also showed those plates to Mary Whitmer, introducing himself as "Brother Nephi."
[Unfortunately, Andrew Jensen, who compiled early Church history, assumed Mary was wrong and changed the narrative to read that it was Moroni who showed Mary the plates. Apparently Jensen didn't know that Joseph had identified the individual as one of the Three Nephites, or that David Whitmer had a conversation with both the messenger and with the actual Moroni and knew they were separate individuals. Nevertheless, to accommodate M2C which claims Cumorah is in southern Mexico, LDS scholars prefer the Jensen narrative, which is not only contrary to the historical records but also highly problematic from a doctrinal standpoint as it promotes the idea that resurrected beings (such as Moroni) can change their shape, age, and overall appearance to mislead mortals (such as by appearing as an old, short, overweight man).]
Back to Ludlow.
In his article, Ludlow reminds us that Joseph Smith explained that "the title-page of the Book of Mormon is a literal translation, taken from the very last leaf... and that said title page is not by any means a modern composition."
Far from being words that appeared on a stone in the hat (SITH), the title page is "a literal translation" taken from a specific leaf of the plates.
Years ago at BYU Education Week, I head one of the educators discuss Church history and actually say, "We don't know how Joseph knew the Title Page was on the last leaf because he didn't even use the plates. They were covered by a cloth when he read the words off the stone in the hat."
That's how absurd the SITH narrative has become.
Ludlow also reminds us that the copyright application of 11 June 1829, and the setting of the type for the title page in "the forepart of June 1829" by Gilbert, both occurred while Joseph was still translating the plates of Nephi in Fayette. Because the Title Page was the last leaf of the plates Joseph had in Harmony, the plates he was translating in Fayette had to be a different set of plates; i.e., the small plates of Nephi that he did not have in Harmony.
The alternative view--that Joseph had the plates of Nephi all along--would require that Joseph did not translate the plates in sequence, that the directions in D&C 10 to translate the "plates of Nephi" were superfluous because he already had the plates, and that the discrepancies in the descriptions of the plates and the different accounts of how Joseph returned them will forever remain a mystery.
But people can believe whatever they want to believe.
See the diagram of the two sets of plates here: