Letter link: Letter from J.R.R. Tolkien to James Heaf • 28 February 1964 (#544)

The exact quote from the auction listing is

I do not think it was an Entwife which Hal saw on the North Moors. Perhaps it was a troll

whereas the summary says "Tolkien does not think it was an Entwife, but likely a troll."

There is a big difference between "I think it was likely a troll" and "perhaps it was a troll". The former makes it sound like he had given some thought to the question and come to a vague conclusion, the latter reads like a vague suggestion with no commitment (unlike the recently uncovered Letter from J.R.R. Tolkien to Jenny Hall • 28 February 1966 (#2927), which makes a very definite commitment; "were meant to be", however, I wholly discount).

Of course, the passage as written was at the time when Tolkien still had giants in Middle-earth, and "tree-men" was almost surely a synonym for them (cf the v. early, pre-Ent Frodo/Treebeard scene where Treebeard is a giant that is described in tree-like terms). So he really didn't have a prepared answer, given on revising the manuscript the given information from cousin Hal was left deliberately vague.

I put it to the letters team that "does not think it was an Entwife, but perhaps was a troll." better reflects the wording as far as we know it from the auction listing.