CathInfo.com

I don't think it's binding to begin with.

But even Ineffabilis Deus, in addition to the Immaculate Conception definition properly speaking, has a lot of other text giving explanations and so on. That Church is not "irreformably" bound to the other text.
Rev. Roberts book was published in 1885, after papal infallibility was defined.  The intro to the version linked above says he denied infallibility.

Yes, Fr Roberts denied the dogma of infallibility. But why did he fall into heresy? Read his book and you will see he shows how and why the 1616 decree was infallible. but, as with them all then, believed it was proven false, a falsification decreed by his pope in 1820. His arguments totally convinced him the 1616 decree was infallible, which the Holy Office of 1820 agreed with (but Roberts did not know this). Such was his faith in the 1616 decree had all the authority of infallibility that he had no choice but reject the 1870 dogma. Had Rome not abandoned the 1616 decree believing it was proven wrong, Fr Roberts, who correctly accepted the infallibility of the 1616 decree would not have fallen into heresy.

Here  is what he said about the Immaculate Conception:

If, then, the Pope said in effect that heliocentricism was a heresy, he said in effect that it was not only de fide, but de fide Catholicâ, that it was false; that it was not only de fide, but de fide Catholicâ, that its contradictory was true. In what capacity he spoke, and whether he meant what he said, are further questions, but it is a great point to have it conceded that he did in effect declare helio­centricism to be a “heresy.” But we also learn from .the statement of a Pontifical Congregation that the utterance was a definition, i.e. a final authoritative judgment. We are brought, therefore, to the conclusion that the Pope did in fact publish, through the Congregation of the Index, a definition of faith. Now, suppose for a moment that he did so ex cathedrâ, would it follow that the definition was of the same kind as that by which Pius IX decided the question of the Immaculate Conception? And ought it to have been promulgated with like emphasis and solemnity? Assuredly not. The definition of the Bull “In­effabilis” was put forward to make that of Catholic faith which confessedly was not so before. Up to the 8th of December 1854 it was, by the force of Bulls that had not been formally revoked, excommunication to call the denial of the doctrine of the Immaculate Conception heresy, or even, if I mistake not, to say that those who impugned it were guilty of grave sin. Since that date, according to the Bull, any one who ventures to think that the doctrine has not been revealed by God, ipso facto, makes shipwreck of his faith, and cuts himself off from the unity of the Church. Clearly the definition was of the nature of a new doctrinal law, and therefore needed a promulgation that would challenge the attention of all Christians. But not every Pontifical definition ex cathedrâ ascribing heresy or repugnancy to Scripture to dissentients is a definition of faith in this sense. By far the greater number are issued, not to generate any fresh obligation of faith, but to protect and vindicate one that already exists [a Pythagorean heresy] ; and to this class obviously belong ex cathedrâ censures of books, and propositions, as heretical. The mode of publishing these judgments will vary of course with circuмstances, but from their nature there is no reason for their being put forward with any greater emphasis and solemnity than the evil to be met requires. Why, then, should they not occasionally be issued through one of the Congregations the Pope has erected to assist him in dis­charging his functions as guardian of the faith? And why should such a mode of publication prejudice their infalli­bility, if they are certainly Papal decisions, and are known to be such?

When the doctrine of the Immaculate Conception was defined, all the conditions of an ex cathedrâ Act were so abundantly and clearly fulfilled that no Roman Catholic theologian would be permitted to raise a doubt on the subject. I do not for a moment pretend that heliocentri­cism was condemned by any judgment of which the same may be said; neither have I attempted to prove that it was.  My contention was a very different one; and I will try to explain and vindicate it.
I found it laid down by such distinguished repre­sentatives of the Ultramontane school as Cardenas, La Croix, Zaccaria, and Bouix, that Congregational decrees, confirmed by the Pope and published by his express order, emanate from the Pontiff in his capacity of Head of the Church, and are ex cathedrâ in such sense as to make it infallibly certain that doctrines so propounded as true, are true.

Similarly, Hans Kung, who also found the 1616 decree was infallible and accordingly claimed the dogma was proven false by way of the same 'proofs' for heliocentrism.

We see then two men were led to reject the 1870 dogma based on that U-turn of 1741-1835 when they too thought the 1616 decree was falsified by science.

So whose fault was it that these two, and many others, rejected the dogma of infallibility?

Here Stanley, maybe this suits your position better than Moses's Genesis and the facts of history.