To quote from an Amy Welborn
post a while back:

we do the dreadful Bernadette Farrell business for the Agnus Dei, the salient portion of which goes,

Jesus, Lamb of God, bearer of our sins, Jesus, Savior: Hear our prayer, hear our prayer, through this Bread and Wine we share, may we be your sign of peace everywhere.

So, the lesson is…they’re going to do what they want anyway. I say let the translators produce produce their fruit, which should be that delicate mix of accurate/poetic/elevated without being fussy or archaic and let the composers cope. It’s not as if they care anyway.

Because, you know, the General Instruction for the Roman Missal, #366, says outright of the Agnus Dei,

It is not permitted to substitute for the chants found in the Order of Mass, e.g., at the Agnus Dei.

…through this Bread and Wine we share….