I think Garfunkel follows the Joan Baez version here. I don't think of that as authentic, largely because I learned another version before hearing this one, and we usually think those the "real" one. I also don't like that he has neither the verse about the father nor the mother, which I consider important. Length, likely, as this is already over five minutes. It was very much the fashion to strive for simple, unadorned interpretations of folk songs, but Garfunkel goes full on in the other direction here - orchestral, modulating up, descant at the end, which I would have predicted I would disdain at the time. Yet I loved it.
I love it more now, and when I sing the song myself it is more influenced by this version than any other.