this is my view (it could be wrong)
some years ago we had what we called the 'truth' book In th first chapter it quotes John 17:3.
Jesus said i am the way and the truth
the gospel is about Jesus. (1cor.15:1-4) and if the anointed witnesses are the body of Christ and they preach the right gospel of the kingdom then they are in the 'truth' irrespective of what things have been taught at times.