Now, the vegetable "pope" (or, rather, non-pope, or material pope) scenario raises some other questions. If the Pope isn't mentally competent, and someone else is signing stuff for him, are those acts really valid? It's similar to the "robo pen" question regarding Biden.
Clearly the answer is no, that if a vegetable pope doesn't know what he's doing, then nothing that others sign on his behalf has any authority.