Joseph Smith's "key" to understanding

There is a lot of unnecessary confusion about the translation of the Book of Mormon.

Joseph explained that he had a key: 

I have a key by which I understand the scriptures. I enquire what was the question which drew out the answer from Jesus, or caused Jesus to utter the parable...

To ascertain its meaning we must dig up the root, & ascertain who it was that drew the saying out of Jesus.

https://www.josephsmithpapers.org/paper-summary/history-draft-1-january-3-march-1843/12

Applying that principle, we should ask what prompted Joseph and Oliver to make the statements they made about the translation. Both of them emphasized that Joseph used the Nephite interpreters that came with the plates. 

Why would they emphasize that? 

The answer should be obvious.

Joseph and Oliver were familiar with the claim made by the 1834 book Mormonism Unvailed that Joseph used a "peep stone" to produce the Book of Mormon. That book claimed Joseph didn't use the plates but instead read words off the stone in the hat (SITH). That rumor persisted enough that Joseph and Oliver clarified the point.

By emphasizing that Joseph used the Urim and Thummim that came with the plates, they refuted claims that Joseph used SITH to produce the Book of Mormon.

They never once stated, suggested, or implied that Joseph used a stone he found in a well or anywhere else.

Example:

the Book of Mormon had come forth as an “ensign to the nations,” containing an account of the gospel in much plainness, being translated by the gift and power of God by the use of the Urim and Thummim, that had come forth with the plates that contain the record.

https://www.josephsmithpapers.org/paper-summary/times-and-seasons-1-september-1842/6

For whatever reasons, many modern LDS scholars/historians now claim that Joseph Smith did not use the Nephite interpreters or the plates to produce the Book of Mormon. Acknowledging what Joseph and Oliver claimed, they rationalize that the term "Urim and Thummim" referred to both the interpreters and the seer stone he found in a well.

Not even the SITH-sayers at the Interpreter, Book of Mormon Central, or FAIRLDS claim that the stone in the hat (SITH), which Joseph found while digging a well years before he obtained the plates, "had come forth with the plates."