So there has never been a definitive decision as to who was the Pope and who was Anti-pope?
But the Point I was making Still stands: Between Boniface IX and Benedict XIII ONE of them was schismatic and an anti-pope. There were saints on both sides of the issues. In other words, you had saints supporting people who were objectively NOT the Pope; and yet they were not considered schismatic.
So, if a sedevacantist, in a similar manner, refuses to recognize Benedict because of his manifest heresy, it cannot be an act of schism. It is an act of prudence and taking the safer course.
The Vatican II God forgives all, so surely he will accept us if we err.
That was my point, and I think it is still a valid one.