Another possibility is that it's just a plot-hole.
I don;t think for a second that the conversation actually took place, the problem of which language the conversation is just one of the clues that it is a work of fiction. Other clues? Well, who recorded the convo if only Jesus and Pilate were the only two people present?
(Was Pilate in the habit of having private conversations with prisoners?)
Not that I am aware of, and also the so-called custom of letting a prisoner go at Passover is laughable and has no foundation in reality. Who in their right mind would think that the Romans would free someone such as Barabbas, an alleged 'notorious' prisoner and possible murderer?
In fact, the whole arrest, trial, and crucifixion narratives reek of fiction.
I recall posting
this topic a while ago, it has some interesting info.
Brian.