The late Fr. William Most actually treats this issue more in-depth than myself:
ewtn.com/library/SCRIPTUR/OUTSID.TXT
Sorry Fr. Most while I respect him, he was extremely prejudiced on this subject and inconsistent with is own principles.
In his article you linked to, he says that we are bound by ONLY the words written and not the intentions of the Magisterium:
“Before going ahead we need to notice one more principle of interpretation.
It is this:** the only things guaranteed in statements of the Magisterium,**
and protected in lesser ways in the works of the Fathers,
are the things
explicitly set down on paper. We may indeed know historically that certain
thoughts, more extensive, were in the minds of the writers.
Yet Divine
Providence has committed itself to protect only the explicitly written
texts, not what is merely in the mind and unexpressed.”
Then he turns around and contradicts this principle
"There are several Magisterium texts that seem quite stringent. The
Profession of Faith prescribed by Pope Innocent III in 1208 A.D. for the
Waldensians says: “We believe in our heart and confess in our mouth that
there is one Church, not of heretics, but the holy Roman Catholic
apostolic Church, outside of which we believe no one is saved.”…
…
Pope Boniface VIII in his famous “Unam sanctam” of Nov. 18, 1302 spoke
strongly: “Outside of which (the Church) there is neither salvation nor
remission of sins. . . . But we declare, state and define that to be
subject to the Roman Pontiff is altogether necessary for salvation.”[22]
The texts of Innocent III and IV Lateran do not go farther than the
patristic texts we have seen. But the second sentence from Boniface VIII
does raise a further question.** However, the difficulty is easily handled;
for the critical line is quoted from St. Thomas, “Contra Errores
Graecorum”: “Ostenditur etiam quod subesse Romano Pontifici sit de
necessitate salutis”[23] (“It is also shown that to be subject to the
Roman Pontiff is necessary for salvation.”) But in the context, shown by
the two quotes St. Thomas gives at this point,** it means merely that there
is no salvation outside the Church. In that sense one must come under the
jurisdiction of the Pope.[24]"
He quotes the “complete” intention of the Pope not just what was written. He says it raises further questions, but only if you don’t accept what is
explicitly written.
There is more but that is enough for now.
He was living in a confusing time in the Church and I can understand his warped loyalty to a supposed Church teaching that doesn’t exist. He was mistaken.