Because translators are biased towards their own doctrinal views is one reason that many present Bible translations are made with translation committees with different doctrinal views. The translators with a different bias can point out the bias of others, and the others can point out the bias of those who point out theirs.
On the other hand, the Church of England makers of the KJV all had the same bias for their Church of England doctrines with no one to balance, point out, correct, or counter their bias.
Concerning John 10:16, Henry Alford, who had a Church of England bias himself, wrote: “The one flock, is remarkable--not one fold, as characteristically, but erroneously rendered in A. V.;--not ONE FOLD, but ONE FLOCK: not one exclusive enclosure of an outward church, but one flock, all knowing the one Shepherd and known of Him” (New Testament for English Readers, I, p. 556). Alford asserted: “The rendering’ fold’ instead of ‘flock’ here is a grievous and important error” (How to Study the NT, p. 152). Alford contended: “It is impossible to acquit King James’ translators of some unfairness here. Tyndale’s version, which they had before them, had the faithful rendering as far as this word is concerned; but they followed the erroneous one” (Ibid.).
Concerning John 10:16 in his Plain Commentary on the Four Holy Gospels, Dean John William Burgon, who also had a Church of England bias, maintained that it should rather have been translated "one Flock, one Shepherd." (Vol. IV, p. 393).