I wasn't sure how to frame the question in the OP, but basically, here's my deal.
Bob attends the Novus Ordo Mass. He as far as he knows believes all dogmas of the Catholic Church, he believes he must believe all dogmas of the Catholic Church and to knowingly reject one would lead to his damnation. But he is simply unaware of the problems with Vatican II.
Bill attends the FSSP Mass. He as far as he knows believes all dogmas of the Catholic Church, he believes he must believe all dogmas of the Catholic Church and to knowingly reject one would lead to his damnation. But while he thinks Vatican II was written vaguely and dangerously, he doesn't believe it per se contradicts tradition if read with a "hermeneutic of continuity". He also doesn't believe New Rite sacraments are invalid.
I mention the SSPV because I've heard Fr. Jenkins say this but... on what basis can any traditional Catholic ordination decide these people aren't Catholic, and refuse them holy communion? How is that not schismatic?
Even if Pope Francis is an antipope and not a real Catholic, for the sake of argument, there are certainly people in "normal communion" with him that truly are in communion with Eternal Rome, despite material errors. I'm not even getting into the una cuм question here. I don't see how denying communion to whole swaths of Catholics doesn't constitute material schism.
The SSPX and SSPX Resistance, on the other hand, despite taking polemical stances against modernism in Rome, seem to recognize that Catholics in good standing can't be denied communion for material errors.
Fr. Jenkins (SSPV, and BTW I like listening to him and respect him, definitely don't mean this as a personal attack) has said that if someone from the FSSP came to his parish for communion he'd deny them communion.
How is that not materially schismatic?
What do you guys think?