Machiavelli says he's an expert in theatre. It's how he claims to have intuited that Knox was guilty, when he saw her in court.
He has never claimed law expertise, really, but he obviously has access to folk who are. He also has access to original documents. Strangely when trying to refute a point (eg. the Satanic Rite theory Mignini once proposed) Machiavelli will claim to have original documents of Mignini's speech (or some such thing) and then does not post it.
Since a de novo appeal's trial is a full blown "re do" of the first level trial, the judge is probably at liberty to accept or reject ANY document or witness, irregardless of whether or not the first trial entered it or refused to. Witness that Massei's court refused to do an independent DNA evaluation, but the Hellmann court overruled that by appointing Conti & Vecchiotti.
As such, the Supreme Court is not supposed to tinker with evidence, just make rulings of law and/or court procedure.
My assumption, and I am not a law expert in ANY country, is that unless Nencini specifically says, for instance, that C&V needs throwing out, that it stays as part of the trial record.
But yes, it would be nice to get a real expert to comment.