Why think that none of the experiences of the three Nephites are genuine?

In 3 Nephi 28 we read:

And when he had spoken unto them, he turned himself unto the three, and said unto them: What will ye that I should do unto you, when I am gone unto the Father?
And they sorrowed in their hearts, for they durst not speak unto him the thing which they desired.
And he said unto them: Behold, I know your thoughts, and ye have desired the thing which John, my beloved, who was with me in my ministry, before that I was lifted up by the Jews, desired of me.
Therefore, more blessed are ye, for ye shall never taste of death; but ye shall live to behold all the doings of the Father unto the children of men, even until all things shall be fulfilled according to the will of the Father, when I shall come in my glory with the powers of heaven.

If this is a true account then we might expect many reported experiences of the three Nephites. D. L. Ashliman reports multiple stories from people who have claimed to experience them.

Are each of these stories fabricated or mistaken?

See:

D. L. Ashliman – The Three Nephites

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