You summarized that well but I would add that charity is more likely to open the gates of heaven than having a perfect knowledge of doctrine. I think that's something we tend to overlook because we have had to defend doctrine and the liturgy from the very church that is supposed to uphold it.
Who makes it to heaven, on an individual basis, is up to God, as only he can read hearts, and only He knows the “whys” of decisions that people make.
But the fact remains that the FSSP accepts V2, the new mass, the new sacraments, etc. They are not Traditional.
It’s not about knowing doctrine “perfectly” (as your strawman fallacy suggested); it’s about how you view the crisis and how you choose to worship God.
Non-Trads believe that V2/new mass are catholic but flawed (as if God can give His Church something which is less-than-perfect). They accept the lie that there can exist both perfection (Latin rite) and deficiency (new mass) at the same time. They accept the heresy that mankind’s sinfulness can tarnish the Divine Liturgy. That God is at odds with Himself, ie old rite vs new rite. Thus, their view of the crisis is preference for the old but acceptance of the new. “Don’t rock the boat.” I’m not even sure they would call the current times a “crisis” as their lives aren’t really affected that much.
Trads, on the other hand, are outcasts, are maligned, are spiritual lepers, because they hold to the one, true Faith; there is only one True Mass. There is only one way to view doctrine. God is not bi-polar, does not contradict Himself and He cannot deceive. He is the same yesterday, today and tomorrow. His liturgical rites are of Divine origin and do not change; they are meant to be for time immemorial; for all peoples; for all places. This crisis in the Church has effected every aspect of the Church and those that reject V2/new mass have suffered, and will suffer all, until God decides to rectify the situation.