Are you suggesting appeal courts write opinions about the facts of the case similar to Italian MRs? I don't think it is common.
ETA - They do write a short summary of the facts of the case.
Both a US appeal court "opinion" and an Italian court "motivation report" give "reasons" for a verdict.
Are you saying that therefore they are similar?
Perhaps you should define what you mean by "similar".
If a novel such as, for example, War and Peace, and a Superman comic book, are both written on paper, does that make them "similar"?
Just pointing out how you sometimes vary your terminology and its degree of precision in order to state what appears as absurdities.
Take the meaning of "testimony" or "testify". You go to a US dictionary to define that term. Yet, the relevance and importance of the meaning of those terms for the AK - RS case is that within the Italian and ECHR legal systems.
For example:
Italian procedural law, CPP Article 62, states:
Any statement made during the proceedings by the accused or the suspect shall not constitute the subject of testimony.
CPP Article 64, paragraph 3-bis states, in paraphrase, if a suspected person has not been warned he shall become a witness (apparently, warned of potential prosecution for calunnia or perjury) by any statement made about the liability of others, the statements that he may have made on the facts regarding the liability of others shall not be used against them, and he shall not become a witness in relation to those specific facts.
Was Rudy warned in accordance with CPP Article 64? Do you have a citation to establish that the Italian procedural law was followed?
In the CPP, there is a section called: Title II Means of Evidence, Chapter I, Testimony, that includes CPP Articles 194 through 207, and is followed by Chapter II, Examination of the Parties, that includes CPP Articles 208 through 212.
But the briefest and clearest statement of the issue with the "testimony" or any statement of Rudy Guede in the AK - RS case is that in the Italian Constitution, Article 111, the relevant part stating:
"The guilt of the defendant cannot be established on the basis of persons who, out of their own free choice, have always voluntary avoided undergoing cross-examination by the defendant or the defence counsel."
In the AK - RS case, the Nencini court attempted to disguise Rudy's unexamined statement as the product of a final and definitive court judgment - Rudy's trial. The Marasca CSC panel, in their motivation report, soundly criticized this as an attempted run-around of the Italian constitutional principle quoted above, and its associated Italian procedural law.
It should be noted for completeness that the Italian principle of not allowing unexamined statements to be used to establish guilt arose from the previous practice of allowing such unexamined statements to be used to establish guilt. This practice led to the ECHR cases of Luca v Italy and Dorrigo v Italy, which helped motivate Italy to modifiy its laws and Constitution to not allow such unexamined "testimony" or statements to be used to establish guilt of an alleged co-conspirator.