I haven't finished reading the document, but
Pastor Aeternus from Vatican I (#4) and
Lumen Gentium from Vatican II both seem to contain criteria for infallibility which lines up with what I was taught:
The Criteria
The five criteria for a teaching to fall under papal infallibility were first taught explicitly by the First Vatican Council in the document
Pastor Aeternus, chap. 4. These can be enumerated as follows.
1. “the Roman Pontiff”
2. “speaks ex cathedra” (“that is, when in the discharge of his office as shepherd and teacher of all Christians, and by virtue of his supreme apostolic authority….”

3. “he defines”
4. “that a doctrine concerning faith or morals”
5. “must be held by the whole Church”
The Second Vatican Council also affirmed this same set of criteria, using somewhat different language, in the document
Lumen Gentium, n. 25. These can be enumerated as follows.
1. “the Roman Pontiff”
2. “in virtue of his office, when as the supreme shepherd and teacher of all the faithful, who confirms his brethren in their faith (cf. Lk 22:32),”
3. “by a definitive act, he proclaims”
4. “a doctrine of faith or morals” (“And this infallibility…in defining doctrine of faith and morals, extends as far as the deposit of revelation extends”

5. “in accordance with revelation itself, which all are obliged to abide by and be in conformity with”
These two sets of criteria are really one and the same. The wording differs slightly, but the teaching is identical.
It seems to me that ex cathedra does not mean that it contains those words.