My next question was going to be about pre/post V2. Pretty big change for the group that claims they don’t change. Good of you to post.
This is dealt with two basic ways. 1. Believe that "The Church" (of Rome) autocratically interprets and defines itself, so that while in the past was asserted "the necessity of belonging to the true Church in order to gain eternal salvation;"
And that [ex cathedra] "it is absolutely necessary for the salvation of every human creature to be subject to the Roman Pontiff;"
And that "whoever abandons the See of Peter on which the Church is established trusts falsely that he is in the Church;"
And that, "in this one Church of Christ no man can be or remain who does not accept, recognize and obey the authority and supremacy of Peter and his legitimate successors;"
And thus "not only pagans, but also Jews and heretics and schismatics cannot become participants in eternal life but will depart into everlasting fire,"
Yet V2 interprets/defines this to mean those
"who believe in Christ and have been properly baptized are put in a certain, although imperfect, communion with the Catholic Church."
"...there are many who honor Sacred Scripture, taking it as a norm of belief and a pattern of life, and who show a sincere zeal. They lovingly believe in God the Father Almighty and in Christ, the Son of God and Saviour. (Cf. Jn. 16:13) They are consecrated by baptism, in which they are united with Christ..."
"they are joined with us in the Holy Spirit, for to them too He gives His gifts and graces whereby He is operative among them with His sanctifying power."
Sources .
2. Deny that such discrepancies can be reconciled, and thus RCs can only obey the papal teaching which requires following leadership as docile sheep if one rejects modern popes as being true popes.