What are you talking about?? The OUM has always been considered infallible. This has always been Catholic teaching.
My religious instruction and readings are 100% pre VatII, and there’s absolutely nothing about the Ordinary Universal Magisterium. Then again, VatII had a penchant for renaming and resplainin’ traditional teaching. My guess is that your education continued after the council, when rather different interpretations came into being along with the puerile & inaccurate American translations of the Latin Mass. I taught from a book called “Lamp of the World” (published, I think, in the early 50s—how’s that for orthodox?) in which it was indeed recognized that bishops ACTING WITH or on behalf of THE POPE in matters of faith and morals shared the inerrancy and infallibility of the pontiff. Big deal. Without the pope, the bishops have nothing but pastoral duties. If it were otherwise, what’s the point of Christ’s appointment of Peter as the Rock?
My Catholicism did survive. With great resentment (to this day). And great trust in all I learned BEFORE John XXIII threw open the doors and windows.