This is part of the risk you take upon yourself when traveling internationally currently. We did a trip VIE-HER-KEF-VIE (with several connecting flights) and, with Iceland requiring a test for entry which we would have to take on Crete, realized we could get stuck in Greece if we tested positive there. It was a financial risk - and one we had to feel comfortable with before we booked. If your friends aren't comfortable with the fact they may get stuck in Italy, they shouldn't travel internationally currently.