In his '71 article he says "Of the three sniper rifles we tested [the other two were Whitworths] the Enfield cal. .45 was the only one which was definitely used in action by Confederate forces." Unfortunately he does not say where or how. Weller says his rifle had a five-groove barrel, while the Kerr had six (I think).
Your comment is well taken though -- the match rifles looked a lot like the service weapons, and like each other, and period descriptions were often vague. I have no doubt that at some of the "Whitworths" were actually something else.
BTW good photo of a match Turner, said to have been used by the South, which utilizes the Whitworth bore. A steal at $7750.