What???
The author is a Jesuit and, therefore, cannot possibly be lacking in knowledge of any topic, including sedevacantism.
Surely you jest.
If this author is a “totally informed Jesuit,” why didn’t he mention “Cum Ex Apostolic Officio?” This encyclical, issued 15 Feb. 1559 by Pope Paul IV (when Robert Bellarmine was only 17 years old), focuses on the validity of a prelate or Pope in the event they are in heresy or apostasy. It says, among other things, that the Pope must be contradicted if he is found to have deviated from the Faith, and that if he has been found to be a heretic, he has no authority. It permits those who should offer him their obedience to withdraw it at any time without being subject to the retribution of any censures or penalties. This Bull was issued “Ex cathedra” and is considered not only infallible, but to be held in perpetuity.
For being so “well-informed,” this Jesuit gives evidence of not being familiar with Papal Encyclicals. His education must not have been all that thorough.