I think it's an important point to bring up because the omission of Greek from the plaque is a key to grasping Gibson's storytelling objectives. The omission has to represent a conscious departure from, not just a historical critical perception of the times (which has been the critique leveled at Gibson for the omission of Greek dialogue), but also a literal Gospel reading, which one might have assumed would be a central Gibson concern if one is thinking that he is simply a Bible literalist. To grasp these objectives is to then understand why Gibson, in addition to omitting Greek speech, prefers a more medieval-sounding Latin over the Latin of Pilate's day. These are not anachronisms born of ignorance.
Did you ever see Terry Mattingly's article on Passion's use of language? Given the cacophony of outcry from language specialists, Gibson appears to be clarifying his earlier assertion about having the movie "tell the truth" in that he now speaks of contrasting "the sacrifice of the cross with the sacrifice of the altar." In seeing the movie and deciphering its rich symbology, it's in an assertion like this that answers about presumed historical mistakes (language choices, wrist nailing, hand washing, and so forth) are to be found.
Excerpt from that article:
It is crucial to realize that the images and language at the heart of "The Passion of the Christ" flow directly out of Gibson's personal dedication to Catholicism in one of its most traditional and mysterious forms - the 16th-century Latin Mass.
"I don't go to any other services," the director told the Eternal Word Television Network. "I go to the old Tridentine Rite. That's the way that I first saw it when I was a kid. So I think that that informs one's understanding of how to transcend language. Now, initially, I didn't understand the Latin. ... But I understood the meaning and the message and what they were doing. I understood it very fully and it was very moving and emotional and efficacious, if I may say so."
The goal of the movie is to shake modern audiences by brashly juxtaposing the "sacrifice of the cross with the sacrifice of the altar - which is the same thing," said Gibson. This ancient union of symbols and sounds has never lost its hold on him. There is, he stressed, "a lot of power in these dead languages."
Thus, the seemingly bizarre choice of Latin and Aramaic was actually part of the message. The goal of Gibson's multicultural, multilingual team was to make a statement that transcended any one time, culture and tongue.
Note: I have moved this from an update on the review post to here for esthetic reasons.