He claims at 1:06:51 that it's a "sententia fidei proxima" (teaching proximate to the Faith) that an interregnum "can't go more than a generation" (1:06:34) because of "the Church's definition that there's a visible Pope" (1:06:57) and "from the First Vatican Council that the Pope is a principle of unity" (1:07:00).
What "definition that there's a visible Pope" is he referring to? And where exactly in Vatican I's Pastor Æternus does it say "the Pope [or Papacy?] is a principle of unity"?
That theological note sounds made up. Like with XavierSem it's probably based on some implicit syllogism that he considers to be airtight. I hold it to be
de fide that the Magisterium and Universal Discipline of the Church cannot fail and lead souls to hell. So there's that. I mean, clearly, the Pope is a principle of unity.
Pastor Aeternus is not needed to tell us this. But based on that "logic," one would have to argue that the Great Western Schism was impossible. Except that it actually happened.