In verse 24, Mormon says that he will make an end of his interjection into the story. However, as with many other times when he makes that statement, he still has something to say. Perhaps, to Mormon, it meant that “I have just a few comments to make at the end.”
He was going to list the names of the three, but was forbidden to do so. Since it is doubtful that any who might meet them in the modern world would know them by their Nephite names, it is perhaps to make sure that we understand that while they had a different mission, the three were not to be exalted over the other nine disciples. All had made righteous choices, and all would receive the same resurrection, and the same exaltation. In modern terms, they would all by inheritors of the Celestial Kingdom.
Verse 26 indicates that almost four hundred years after their transformation, they ministered personally to Mormon. Mormon was therefore a disciple who could witness to the Savior because he had spoken directly with those who had been there, and there were three which even exceeded the requirement to establish truth in at least the mouth of two.