It has a philosophical aspect to it. We habitually interpret this affirmation concerning the apostolic life of Jesus. If it were referring to his apostolic life, Jesus would have said that he came to bear witness that he is the Son of God. For Pilate, however, that Jesus be the Son of God means nothing. One must not forget that in Rome, in those days, the philosophy of Epictetus, a stoic philosopher, reigned.
Stoic philosophy seeks truth, practical truth.
Jesus doesn't use his spiritual authority with Pilate. Pilate would not have understood. Even less would he have understood temporal authority, for it is outside of his perspective. He can, however, speak of truth, and he does speak this clear and precise language regarding the authority of Pilate. Not at all.