I not only read it, I redlined it. It is not what you think it is. Indeed, it could not be. It is about epistemology, not dogma and was part of the failed project by Pio Nono to hold back modernity in thought and create a papal privilege in academia to give the Pope primacy in his turf, even when the facts disagreed with teaching. Your belief in that enduring claim has a name: arguing from authority. It is a logical fallacy.
http://xianleft.blogspot.com/2017/09/dei-filius-annotated-modernistically.html