True, they start off with that question, but in the 3rd paragraph they raise the questions:
Who, then, were the “sheep” of the fold that
would form “one flock” with the “other sheep”? Would they be the
Jewish disciples, whereas the “other sheep” would be the Gentiles who,
in time, were accepted as anointed Christians?
They then proceed to the discuss the gentiles / "other sheep" issue before returning to the original question.