My grandmother had a brain tumor. After surgery they said she wouldn't wake up for a week due to brain swelling. However, they warned us that she could still hear and understand. Apparently this is the norm for people in comas. I'm surprised the Italian doctors didn't know this.
Perhaps because he was in a coma for two years they were projecting long-term. A week/ your grandma's surgery, that is one thing, a short objective. As a coma drags on and on and the doctors don't see improvement or hope, I imagine one sees it so differently.
My mother also had a brain tumor, and had the same experience. She has recounted conversations that the nursing staff had, including dirty jokes they told. Trust me, my mother didn't imagine dirty jokes. She was a Dean of Women at a Christian College.